san_acacia

San Acacia Reach Restoration Project

=Hydrology - Cameron Herrington= =Hydrology of the San Acacia Reach =

The Rio Grande River becomes part of the San Acacia Reach once it reaches the San Acacia Diversion Dam and continues downstream to the Elephant Butte Reservoir next to Truth or Consequences, New Mexico (Figure 1). The reach length is approximately 70 miles long and flows through this section are split at the diversion dam into the main river channel and a low-flow conveyance channel that parallels the river down to Elephant Butte. Most of the reach has agricultural lands that border the river on its western side and the section contains the communities of San Acacia, Socorro, and San Antonio. In addition to the flow diversion from the river within the conveyance channel, there are also agricultural withdrawals from the river that are contained in riverside drains and the larger Socorro drainage channel. Flows within this reach have the ability to reach no flow conditions during the driest periods of the year as there are no present controls on maintaining minimum flow amounts through the San Acacia section of the Rio Grande River.



Figure 1- New Mexico map showing location of San Acacia reach between San Acacia and Elephant Butte Reservoir (Padilla and Baird 2010).

Historical Perspectives on the San Acacia Reach
San Acacia generally catches the tail-end of the flows within the Middle Rio Grande Valley. Much of the water available through the river is allocated to the upstream communities in the Albuquerque Area and agricultural zones within Valencia County prior to its entrance into the diversion structure at the top of the reach. The lack of attention placed on this river zone is somewhat a function of its isolation from the main urban centers within the state as well as the extent of the historical floodplain in this area and its tendency to experience large flood events before the construction of the Cochiti Dam in 1973.

Flows in the San Acacia reach are not monitored as closely as other regions upstream. The United States Geologic Survey (USGS) currently only has two active gages that are operational within the main river channel, the floodway gage at San Acacia and another located in the narrows area of the river just above the Elephant Butte Reservoir. There are also two gages in the low-flow conveyance channel that have been in operation since 2005 located at San Acacia and San Marcial. The low-flow conveyance channel (Figure 2) construction was completed in 1959 and occurred in response to flooding events in the 1940’s that completely filled the Elephant Butte reservoir and resulted in inundation of the tributaries within the river delta around the Bosque del Apache area. This deposited a large amount of sediments into the river outfall and made it difficult for New Mexico to meet compact deliveries to Texas. For much of the 1960s and 70s, the entire river flow through the reach was carried within the conveyance channel that held a 2000 cfs capacity (Gorbach 1999). Any flows above this value were still directed into the main river channel.

Figure 2 – Aerial view of the San Acacia Diversion Dam diverting flows from the Rio Grande River to the low-flow conveyance channel in San Acacia, New Mexico.

Operation of the low-flow conveyance channel continued in this manner until large flooding was experienced in the region once more in the 1980’s. The reservoir became filled to capacity as it did in the 40’s and again plugged both the main channel and this time the conveyance channel as well with deposited sediments. The levee that had been placed between the river and the conveyance channel to protect it also served to constrain the main river channel to the floodplain east of the levee. This resulted in the main channel becoming perched above the conveyance channel and a head difference between the two of about 10-15 feet (Gorbach 1999). The operation of the conveyance channel for delivery of compact water ceased in March of 1985. River agradation in the lower portion of the San Acacia reach has proved to be a large challenge for regional water planners.

Climate Change in the Middle Rio Grande Basin
The San Acacia reach has experienced alternating average flows of 1,100,000 and 570,000 acre-feet throughout the water record (Padilla and Baird 2010). Of course the drier years hover around the lower value of the range and this is the period that we currently find ourselves in. Current understanding within the scientific and hydrological community is that the consequences of the anthropogenic release of carbon dioxide into the atmosphere will result in the increase of average global surface temperatures of between 1.5 and 7 °C (IPCC 2013). Increases in surface temperature are expected to result in significant shifts in the seasonal flow regimes within the Middle Rio Grande Basin as well as higher evaporation rates and more severe drought and flooding cycles (Llewelynn and Vaddey 2013). Water availability for most of the source inputs to the Rio Grande River is expected to fall by about a third overall, and the San Acacia section of the river has already recently been subjected to periods of no-flow drying conditions (as measured at USGS gage 08358500 in San Marcial, August-September, 2003). All of these factors indicate a continued stress that will be placed on the water system in the San Acacia reach and the need for engineered solutions in regards to river restoration or management.

Current Hydrology of the San Acacia Reach
The river reach between San Marcial and Elephant Butte Reservoir continues to face the challenges placed upon it by aggradation. Compact flow deliveries are being made through the main channel reach and channel dredging operations are the primary means to minimize loss of flows due to them spreading out onto the floodplain. This delta region of the reach, while not being as suitable for preventing conveyance losses for compact deliveries, is quite beneficial habitat for migratory bird species such as the willow flycatcher. The reach just downstream of the San Acacia Diversion Dam and upstream of San Marcial is in an opposite state of channel response and experiencing incision as a result of the structure itself creating an artificial gradient in the river’s bed slope; however, the lower reach aggradation is considered to be the largest restoration challenge in this section of the river.

Although the low-flow conveyance channel is not utilized any longer for the Rio Grande Compact deliveries to Texas, it remains a vital flow source for the Bosque del Apache National Wildlife Reserve (NWR). It also serves as a river drain system and carries return agricultural flows to the Elephant Butte Reservoir (Gorbach 1999). Habitat within the NWR does benefit from the increased floodplain connectivity caused by the channel aggradation below San Marcial and the ecosystem services that have become available through any river management failures at increased channelization of the river system need to be considered in future habitat restoration efforts.

The hydrograph through the San Acacia reach suffers from the decreased attention it receives when compared to the upstream sections. Minimum flows are not maintained in the Rio Grande River channel below the Central gage in Albuquerque. The temporary lack of flow within the river between San Marcial and the Elephant Butte Reservoir in late summer both encourages sediment deposition within the floodplain delta following monsoonal runoff from the region’s surrounding bluffs and restricts the ability to establish a healthy habitat for other endangered species such as the silvery minnow by maintaining a river flow throughout the year. The river is simply drained of its ability to clean out the sediment due to upstream water extractions and flood control.

Restoration Possibilities from a Hydrological Viewpoint
Much of the San Acacia reach below the diversion dam could be viable habitat for sustaining both minnow and flycatcher populations if it were able to receive some sort of minimal flow throughout the year. The area is not populated by large urban centers and much of the natural floodplain connectivity still exists along the river channel if it were to receive overbanking flows. The main restriction to allowing lateral movement of the channel is the existing low-flow conveyance channel that was constructed in the 1950’s and has not been serviceable for the last 30 years. It appears that the primary challenge for restoration efforts in this reach is to develop a solution that can minimize the impact of channel aggradation due to sediment deposition. Currently, regular dredging of the channel is required in order to effectively deliver the water volume to the Elephant Butte Reservoir as is mandated by compact agreements between New Mexico and Texas. Engineered efforts such as the low-flow channel to this point have proved to remain ineffective and have served to limit ecosystem services in the region.

Much of the reach’s sediment load that is not already contained within main channel flows enters through the Rio Puerco and Rio Salado outfalls just north of the diversion dam at San Acacia. Both of these arroyo systems are intermittent streams that only flow during monsoonal rainfall events that are common in the summer months in New Mexico. Global climate change predictions indicate that the region’s storm events will become both more intense and that the precipitation type will change from mountain snowpack to rainfall as surface temperatures climb and the atmosphere is able to hold a greater water content (IPCC 2013, Llwelynn and Vaddey 2013). This might indicate that generally dry arroyo systems such as the two described above might flow at higher volumes than they do now and at different months that they have historically. This could increase their ability to transport sediment into the system which should be mitigated for purposes of downstream water conveyance while also providing an opportunity for increased water storage in the region from the runoff generated by localized storm systems that is not accounted for in the water allocation of the Rio Grande Compact Agreement. Overtime this storage could become significant and could possibly serve to maintain minimum flows within the San Acacia reach while also protecting the basin as a flood control mechanism against flashy storm events.

Silvery minnow - Ray Holland


 * The Rio Grande Silvery Minnow in the San Acacia Reach **

The San Acacia reach of the Middle Rio Grande is an important segment of the remaining range of the endangered Rio Grande silvery minnow. A significant portion of the silvery minnow population currently exists in the San Acadia reach, possibly because the eggs and larvae are carried downstream by the current but the diversion dams generally prevent the adults from swimming back upstream. Although this reach of the river supports a relatively large number of minnows, the river is allowed to completely dry in some areas of the San Acacia reach most years for up to three months in the summer. The Rio Grande silvery minnow (Hybognathus amarus) was listed as endangered by the US Fish and Wildlife Service (FWS) in 1994 and the New Mexico Department of Game and Fish in 1996. The silvery minnow was one of the most widespread and numerous fish in the Rio Grande system with an historic range extending from the Gulf of Mexico upstream to north of the confluence with the Rio Chama and up the Chama to Abiquiu, as well as in portions of the Jemez River and the Pecos River, both tributaries of the Rio Grande. The current range, which is limited to the middle Rio Grande, extends from the delta of Elephant Butte reservoir upstream to the Angostura diversion dam below Cochiti reservoir, only 5% of the historic range. The critical habitat area designated by FWS extends from Cochiti dam downstream 212 miles to the utility line crossing the river upstream of the Elephant Butte delta and up the Jemez River to Jemez Canyon dam excluding pueblo lands, essentially the current range. The San Acacia reach is an essential part of the designated habitat.


 * Minnow Characteristics and Habitat Needs **

Over the past three decades, the habitat needs and biological characteristics of the Rio Grande silvery minnow (RGSM) have been extensively studied. However, since many important river characteristics of the middle Rio Grande (MRG) including flow regime, sinuosity, river-floodplain connectivity, water quality, channelization, water quantity, native species competition, and introduced species competition had already been significantly altered, it is not possible to determine ideal natural conditions. At this point we are attempting to develop the best recovery plan within the realistic constrains of the current middle Rio Grande. Silvery minnows thrive in warm, shallow, meandering streams with significant habitat heterogeneity. Diverse aquatic habitats have historically included intermittent side channels formed by spring overbanking, ever-changing both sandy and vegetated bars and islands, eddies, bank irregularities, sand, silt, cobbles, some boulders, and accumulations of woody materials. The minnows have adapted to a varying hydrograph including high spring snowmelt peak flows which cue RGSM spawning and maintain diverse, off-channel habitat during an extended period of moderate flows, very low summer flows, and late summer monsoon intermediate to high flows. Historically, the high spring flows initiate spawning and create diverse, off-channel nursery and juvenile habitat. Spawning will usually occur with flows of 2500 to 3000 cfs for about five days and population success is likely if the five days is followed by approximately 25 days of flows around 1500 to 2000 cfs. As long as the elevated flow continues, most of the young minnows will remain in the off-channel habitat. The slower moving, warm water with ample sun and relatively stable substrates such as cobbles and wood debris of these backwaters, ephemeral pools and side channels are ideal habitat for the preferred minnow diet of algae, larval insects, plant material and organic sediment. Early success and adult size of the minnows is correlated to availability of algae and diatoms for the young silvery minnows. Since the RGSM is an important element in the MRG food web, minnow food habitat affects the entire MRG ecosystem. The RGSM populations are more successful when the floodplain remains inundated through the larval and into the juvenile stage. Receding floods trap the young minnows, eventually killing most all that remain in the side channels. Ideally, the descending leg of the hydrograph will extend for 3 to 4 weeks, allowing the newly hatched minnows to gain enough size and strength to survive in the open channel.


 * Threats to the Silvery Minnow **

However, this ideal is almost never achieved in recent years. Fourteen of the 27 native MRG fish species have recently gone extinct as a result of anthropogenic river modification. The many threats to the Rio Grande river system include these threats specifically impacting the silvery minnow. The altered flow regime designed to satisfy the needs of irrigation and compact deliveries has almost eliminated floodplain-inundating peak flows and frequently results in dewatering of some stretches of the San Acacia reach from July to September. Habitat fragmentation resulting in vulnerable populations and reduced genetic diversity is brought about by lack of longitudinal connectivity because of reservoirs and diversion structures. Although they are strong swimmers capable of moving upstream, few adult minnows make it to the upstream reaches. Larger numbers of fish are found in the northern portions of the sub-reaches below diversion dams. During the spawning season, historically, most eggs and larvae ended up in the side channels and ephemeral wetlands. Those eggs and larvae which were floating down the main channel might be carried by the current into one of these side channels. With reduced peak flows precluding most overbanking, floodplain inundation, and floodplain connectivity, eggs and larvae drifting down the channel now generally end up in irrigation ditches, the low flow conveyance channel, or Elephant Butte reservoir, where they will find no cover and probably become someone’s lunch. Water quality is degraded by municipal, industrial, and agricultural discharges upstream and nonpoint source agricultural inputs of nutrients and pesticides in the San Acacia reach. The RGSM has co-existed with native predators such as the Rio Grande chub and bluegill, but since the late 19th century, its list of predators has included several introduced species including red shiners, which are believed to aggressively prey on the young minnows. Competition for limited resources from three introduced minnow species also impacts the RGSM. Channelization, channel straightening, and flow regulation have greatly diminished available minnow habitat. The San Acacia reach has very little sinuosity and overall river complexity which could provide low velocity off-channel habitat. To keep the water flowing to meet compact deliveries, we have removed flow impeding channel structures such as woody debris, islands, bars, and side channels, eliminating most sources of minnow habitat.


 * Restoration Possibilities for minnow recovery **

We have identified these priorities for the Rio Grande silvery minnow restoration effort in the San Acacia reach of the middle Rio Grande in order to continue to maintain a wild minnow population. 1) We must maintain sustained flows throughout the entire San Acacia reach. 2) Pulse flows are needed every spring for spawning and off-channel habitat creation. 3) Nursery and juvenile habitat is needed for feeding and cover, preferably off-channel, but if necessary in–channel. 4) Re-establish longitudinal continuity by constructing San Acacia fish passage structure.

1) Sustained flows – In recent years the San Acacia reach has been home to a significant portion of the limited remaining RGSM population. Yet we continue to allow river drying in the San Acacia reach. Only 50 cfs is required to remain in the river below the San Acacia diversion channel, according to the 2003 Biological Opinion. The river is fully appropriated and the remaining flow except 50 cfs is diverted at San Acacia. This nominal 50 cfs for the minnow is quickly lost to infiltration and evaporation. We must allow sufficient flow through the San Acacia dam to maintain that minimum 50 cfs all the way to the delta of Elephant Butte reservoir. The minnows survive in this already fragmented habitat because we collect them in the drying ponds and move them to areas with water or the refugia. If we are to have a sustainable wild population, we must have water in the river. Justification for diverting the entire flow of the river is based on the assumption that certain areas of the MRG dried up on a regular basis. But when the river was free flowing, there were side channels, ephemeral pools, and wetlands all along the San Acadia reach. We now have a simple channel with almost no off-channel habitat. The minnows have no place to go to escape the drying channel. We also must address the water lost by seepage into the low flow conveyance channel.



Floodplain- Bosque del Apache NWR

2) Pulse flows are needed each spring for spawning and, when possible, overbanking. After studying the results of several pulse flow attempts, we recommend a minimum spring pulse flow of 3-4000 cfs at the San Acacia dam for 5 days followed by 1500-2000 cfs maintained for approximately 25 days. The maps show areas that may flood at 3000 cfs (light pink) and 4000 cfs (blue). Substantially more habitat can be created with 4000 cfs, but a significant amount can be established with 3000 cfs. 1500-2000 cfs for the next several weeks will result in a recession rate which will maintain the habitat until the young silvery minnows are established.





3) We strongly recommend spring pulse flows to establish and maintain spawning, nursery, and juvenile habitat. If the water is not available, a possible alternative is to create in-channel minnow habitat by constructing large woody debris (LWD) structures. LWD has been used in other river systems to create fish habitat but is unproven in the Rio Grande. LWD can be used to create diverse habitat by mimicking natural logjams. Trees, logs, and/or rootwads are anchored to the bank and riverbed. Water flowing over and under LWD can form scour pockets which provide cover and low-velocity habitat. Pools remain wet longer during low flow periods. Wood, branches, and organic material may accumulate, resulting in diverse fish habitat. We recommend the construction of the San Acacia dam fish passage structure which has been =2. River Geomorphology - Matias Mendez=

The terms //river // morphology and its synonym fluvial //geomorphology // are used to describe the shapes of //river //channels and how they change over time. An understanding of the processes of water and sediment movement in river catchments and channels and their floodplains – together with the forms produced by those processes – is an essential component of sustainable fluvial projects. This understanding primarily comes from the discipline of fluvial geomorphology, which is becoming established as good practice in the feasibility, appraisal and design. Fluvial geomorphology integrates with other disciplines and helps to bridge the gap in understanding between the specialisms. The assessment of potential ecological impacts and their mitigation and the development of sustainable engineering design require the expertise of a geomorphologist. 

Figure 2.1 Interrelationships of fluvial geomorphology


 * Middle Rio Grande **

The Rio Grande has been the source of life-giving water for civilizations in New Mexico for as long as people have lived here. By the 1920s, the bed of the Rio Grande had become higher than the surrounding land. Heavy diversions of water from the river in Colorado made it less able to carry away silt. That silt built up in the Middle Valley. As a result of the river being higher than the surrounding land, water from the river leaked into the surrounding land and turned it into a giant marsh. The MRGCD’s ditches drained the Valley and made it suitable for agriculture and development. 

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Photo 2.1 1920’s Rio Grande

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Water management has altered the balance in hydrologic and sediment processes throughout the Rio Grande basin. Projects such as mainstem and tributary reservoirs, channelization, levee construction, channel stabilization, and water diversions implemented in the past 100 years have affected the channel shape, size, and sinuosity. Most of the levee system, riverside drainage canals, and small diversion dams in the MRG Valley were built in the 1930s (Massong, et al., 2002). The San Acacia Diversion Dam was built in 1935. Some jetty jacks were constructed by MRGCD as early as the 1930s, including those just below the San Acacia Diversion Dam. MRGCD constructed extensive earthen and timber channel training structures in the 1930s. The large upstream dams and jetty jack systems were constructed between 1953 and 1974. Significant upstream storage began around the turn of the 20th century and concluded with the construction of Cochiti Dam in 1974.


 * <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Sediment Supply **

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Data from two USGS Rio Grande stream gages, San Acacia (# 08354900) and San Marcial (# 08358400) determine the water discharge-suspended sediment history. Discharge for the San Acacia gage dates from 1936 to the present, while suspended sediment only dates back to 1949. The San Marcial gage has a more extensive record, with discharge data collected back to 1895 and suspended sediment back to 1925. The volume of both water and sediment has varied greatly throughout the period of record for both the San Acacia and San Marcial gages.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Flows are higher in May and June (Figure 2.2), and the large sediments comes in august (Figure 2.3).

<span style="font-family: 'Arial','sans-serif'; font-size: 16px; line-height: 0px; overflow: hidden;">

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Figure 2.2 Average Monthly Discharges at San Acacia <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Figure 2.3 Average Monthly Suspendent Sediment at San Acacia

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Annual trends of the quantity of water and suspended sediment passing the San Acacia gage indicate that the total yearly amount of water increased in the 1980's (Figure 2.4) while the amount of sediment has steadily decreased since 1980 (Figure 2.5).

<span style="font-family: 'Arial','sans-serif'; font-size: 16px; line-height: 0px; overflow: hidden;">

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Figure 2.4 Annual discharge given in year discharge and cumulative <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Figure 2.5 Annual sediment load given in year discharge and cumulative <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Figure 2.6 Discharges vs. Suspended Sediment

<span style="color: #000000; font-family: 'Arial','sans-serif'; font-size: 16px;">Total sediment discharge (tons/day) was then plotted as a function of flow discharge (cfs) for each gauging station. This relationship between sediment discharge and flow discharge is used to assess the appropriateness of the transport equation. The range of discharges run through SRH-Capacity is reflective of the water year 1975, so the discharges do not span the domain of discharges associated with the stream gauge measurements.

<span style="color: #000000; font-family: 'Arial','sans-serif'; font-size: 16px; line-height: 0px; overflow: hidden;">

<span style="color: #000000; font-family: 'Arial','sans-serif'; font-size: 16px;">Figure 2.7 <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">San Acacia gauge

<span style="color: #000000; font-family: 'Arial','sans-serif'; font-size: 16px; line-height: 0px; overflow: hidden;"> <span style="color: #000000; font-family: 'Arial','sans-serif'; font-size: 16px;">Figure 2.8 <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">San Marcial gauge


 * <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Geomorphic Trends **

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">There has been a significant reduction in sediment supply when compared to the early part of the 20th century (Table 2.1 and Table 2.2). The reduction in upstream sediment supply has contributed to the reduction in the active channel width and impacted such features as mobile sand bars, movement of large-scale macro-form bars, and channel migration across the active floodplain. A less active channel results in sand bars becoming stabilized with vegetation. Overtime, vegetated sandbars can vertically accrete with sediment deposition and become attached to banks and islands. The process of channel narrowing due to the altered relationship between sediment and water discharge and subsequent vegetation encroachment in the active channel is progressive and is the foremost change in the channel morphology. Previously, wide sections of channel of over 1,000 feet have diminished to an active channel 300 feet or less.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Table 2.1 Reduction in Sediment Load Concentration <span style="font-family: 'Arial','sans-serif'; font-size: 16px; line-height: 0px; overflow: hidden;">

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Table 2.2 Reduction in Mean Annual Sediment Load

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">The Escondida Sub-reach is not currently displaying any significant incisional pattern and may have reached slope equilibrium where the sediment supply to the reach is approximately equal to the sediment transported out of the reach. The reach has recently displayed renewed channel migration, bank erosion, and channel widening, which could be a response to approaching sediment transport equilibrium. The bank erosion has ecosystem benefits of providing significant quantities of sand and large wood debris to the downstream reaches. The San Antonio Sub-reach has been in slope equilibrium status for a relatively longer period. This sub-reach also displays some bank erosion and has areas showing increased channel migration.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px; line-height: 0px; overflow: hidden;">

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Photo 2.3 Woody Debris Deposited in San Antonio Reach

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">The sediment supplied by arroyos and erosion of the channel bed/banks dominates the current local supply of sediment. Wells drilled during the building of San Acacia Diversion Dam in the 1930’s and a ground water study in the early 1990’s (unpublished USBR data, 1930’s, and

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">1993) found that although sand-sized sediment dominated the channel bed and bank deposits, gravel was also present. The gravel measured indicate that gravel sized sediment was transported in the Rio Grande, at least episodically. Further downstream found less gravel than at the dam, which may indicate that the gravel layer was spatially isolated and mostly located near its source, the Rio Salado, rather than reach wide.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;"> <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Figure 2.9 Sub-Reach location map showing Sub-reaches 1, 2, 3 and 4 Rio Grande – San Acacia Reach

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Large arroyos currently supplying sand and gravel sized sediment include the Rio Salado, Arroyo Alamillo and Arroyo de la Parida. Although the Rio Salado enters the Rio Grande just upstream of the study reach gravel transports to the mainstem are currently transported downstream of San Acacia diversion dam. Although historic levels of Rio Salado sediment supply are unknown, the size and present extent of the Rio Salado alluvial fan is similar to that found in earlier 1935, indicating that the supply of sediment may have been similar throughout the 1900s. Current sediment sizes found in the Rio Salado alluvial fan consists dominantly of sand and gravel (Table 2.3), however cobble sized sediment from the Rio Salado were found in the Rio Grande channel immediately downstream of the confluence. Two medium-sized arroyos, Arroyo Alamillo and Arroyo De La Parida currently enter into the Rio Grande. Both these arroyos transport sand, gravel and larger sized particles (Table 2.3) to the Rio Grande. San Lorenzo Arroyo, which historically meets the Rio Grande, was disconnected from the Rio Grande when the LFCC channel was built in the 1950s/1960s. These tributaries and relic sediment deposits in the channel bed/banks are important local sediment sources for the Rio Grande, but especially important as local sources of gravel.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Table 2.3 Samples of bed material from tributaries within or near the San Acacia Reach <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Material is added to the channel by two major processes: collapse of arroyo walls and piping. Collapse occurs when wall materials are weakened and saturated either by channel flow or by local precipitation. Piping occurs when local precipitation flows into the soft arroyo wall materials and encounters favorable flow paths that are enlarged until they become voids. In some places piping has created voids that can swallow automobiles. Once introduced into the channel, the disrupted wall materials are readily transported by the stream during periods of high flow. The relative volumes of material that are produced by collapse and piping are unknown.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;"> <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Figure 2.10 Sediments by tributary in Tons

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">The following photo is at The Rio Puerco at the Interstate 40 crossing exhibits arroyo walls with slumps, vegetated terraces, and natural levees along the margin of the inner channel. The slumping arroyo wall is approximately 6m high. <span style="font-family: 'Arial','sans-serif'; font-size: 16px; line-height: 0px; overflow: hidden;"> <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Photo 2.3 Rio Puerco

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Erosion is a problem endemic to semi-arid lands. In more humid climates, vegetation holds soil in place, limiting the amount of material that can be carried down hill slopes and into rivers and streams. In extreme arid climates there is insufficient flow to transport sediment. It is in semi-arid lands - where there is incomplete vegetation cover yet sufficient water to move surface materials, especially during and after intense rain storms - that maximum sediment is carried downstream. <span style="font-family: 'Arial','sans-serif'; font-size: 16px;"> <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Figure 2.11 Potential Erosion Rio Puerco

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">The Rio Puerco basin of New Mexico lies due West of Albuquerque. The Rio Puerco is a tributary of the Rio Grande; at the confluence the Rio Puerco contributes about 4% of the annual water flow and about 78% of the sediment. <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Why is the Rio Puerco a particularly high generator of sediment? <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">First, it is in the range of annual precipitation that produces maximum sediment (see sediment yield curve and erosion vulnerability map). Second, a large fraction of the Rio Puerco Basin is composed of shales and siltstones that erode readily, creating areas of high sediment yield that contribute to a large store of fine-grained, easily-eroded, valley-fill materials. Third, the Rio Puerco basin has substantial topographic relief; high terrain helps to generate precipitation and steep slopes provide sediment-moving power to the resulting runoff. Fourth, the Rio Puerco basin is prone to large thunderstorms during the summer monsoon season; annual precipitation is concentrated in a few events that are capable of moving large quantities of sediment.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;"> <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Photo 2.4 Rio Puerco at dry conditions

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;"> <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Photo 2.5 Rio Puerco at wet conditions

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">The two most important concepts behind geomorphology are:
 * <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Sediment Control Solutions **

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">- Conservation (maintaining or restoring natural morphology and habitats); <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">- Sustainability (minimizing maintenance and cost).

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">It is necessary to consider the sustainability of such works, not only from the geomorphological perspective, but also in terms of the achievement of the hydraulic aims and the whole-life costs. <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Develop some sediments controls in the upper stream of San Acacia diversion dam is a solutions to manage the sediments in our reach. Create the sediment control, in the upper part of the reach will be better than create solutions after the dam. <span style="color: #000000; font-family: 'Arial','sans-serif'; font-size: 16px;">Implementing this strategy would involve sediment removal, sediment exclusion, or sediment augmentation depending on whether the reach tends to be aggrading or degrading. Theoretically, the amount of sediment added or removed from the reach would be just enough to establish a balance between sediment supply and the sediment transport capacity of the reach. If a balance is established, it is assumed that minimal channel adjustments would occur, and therefore, the baseline condition geometry (BASE) is sufficient to represent the geometry for this strategy. This strategy assessment does not consider sediment sizes for augmentation at this stage of analysis, only volumes. <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">The potential construction and operational impacts of creating sediment controls are:

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">- Sediment regime, regulate impacts to the riverbed over the reach due to accelerated deposition or erosion and/or impacts to sensitive species or habitats as a result of changes to suspended sediment load or turbidity <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">- Channel morphology, impacts to the diversity of channel morphology, with consequences for ecological quality <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">- Natural fluvial processes, interruption to the fluvial processes, such as channel planform evolution or erosion and deposition

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">By permanently stabilizing the disturbed areas as soon as possible after construction is complete in those areas, you can significantly reduce the amount of sediment which should be trapped before it leaves your site. An area can be stabilized by permanent seeding and planting, sediment trap, gradient terraces and gravel or stone filter berm.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Permanent seeding of grass and planting trees and brush provides stabilization to the soil by holding soil particles in place. Vegetation reduces sediments and runoff to downstream areas by slowing the velocity of runoff and permitting greater infiltration of the runoff. Vegetation also filters sediments, helps the soil absorb water, improves wildlife habitats, and enhances the aesthetics of a site. Improves the aesthetics of a site, provides excellent stabilization, provides filtering of sediments, provides wildlife habitat and is relatively inexpensive.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">A sediment trap is formed by excavating a pond or by placing an earthen embankment across a low area or drainage swale. An outlet or spillway is constructed using large stones or aggregate to slow the release of runoff. The trap retains the runoff long enough to allow most of the silt to settle out. Protects downstream areas from clogging or damage due to sediment deposits, is inexpensive and simple to install and can simplify the design process by trapping sediment at specific spots onsite.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Gradient terraces are earth embankments or ridge-and-channels constructed along the face of a slope at regular intervals. Gradient terraces are constructed at a positive grade. They reduce erosion damage by capturing surface runoff and directing it to a stable outlet at a speed that minimizes erosion. Hold moisture better than do smooth slopes and minimize sediment loading of surface runoff.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">A gravel or stone filter berm is a temporary ridge constructed of loose gravel, stone, or crushed rock. It slows and filters flow, diverting it from an exposed traffic area. Diversions constructed of compacted soil may be used where there will be little or no construction traffic within the right-of way. They are also used for directing runoff from the right-of-way to a stabilized outlet, is a very efficient method for sediment control.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Geomorphology (understanding of channel form and processes) plays a key role in river management problems and solutions, and is essential to achieving the requirements of habitat restoration.

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">References

<span style="font-family: 'Arial','sans-serif'; font-size: 16px;">- River Restoration Class - <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Middle Rio Grande Conservancy District - <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Geomorphologic Assessment of the Rio Grande San Acacia Reach Restoration Analysis and Recommendations for the San Acacia Reach of the Middle Rio Grande, NM - <span style="font-family: 'Arial','sans-serif'; font-size: 16px;">Geomorphological change and river rehabilitation, H.P. Wolfert - <span style="color: #000000; font-family: 'Arial','sans-serif'; font-size: 16px;">Middle Rio Grande River Maintenance Program Comprehensive Plan and Guide <span style="color: #000000; font-family: 'Arial','sans-serif'; font-size: 16px;">- United States Enviromental Protection Agency

=Southwestern Willow Flycatcher - Raphael Perea= In 1995, the U.S. Fish and Wildlife Service (USFWS) listed the Southwestern Willow SWFL as an endangered species. In correlation with their breeding range SWFL has been listed as an endangered species or a species of concern in Nevada, Utah, Colorado, California, Arizona, New Mexico, and Texas. Critical habitat for the SWFL is broken up into three parts along the Middle Rio Grande (MRG), separated by the Sevilleta and Bosque del Apache. San Acacia has two documented (SWFL) territories in Escondido and Elephant Butte Marsh. The Escondida area is historical and was first cited in in 1964. The Elephant Butte area is the primary nesting site for SWFL studied since the 1970s. From late July to August, SWFLs migrate as far down as northern South America for the winter and return to breeding grounds around May to early June. SWFLs nest from May-June and require two weeks to and develop into fledglings. After fledglings live with their parents for two more weeks little is known of their activity.
 * Southwestern Willow Flycatcher **

The middle Rio Grande has two distinctive sets of vegetation. The first set contains primarily cottonwoods and a few willows. The next set contains smaller meadow-like vegetation growing in mud banks containing cottonwoods, willows and cattails. SWFLs are rarely present in vegetation patches less than 10m. SWFL can consume small fruits and berries, they tend to be insectivores. SWFLs usually eat insects of terrestrial birth as opposed to aquatic ones with the exception of dragonflies and damselflies. Flycatcher fecal matter contained remains of bees, wasps, leafhoppers, beetles, lady bugs, dragonflies, and damselflies. This highly variable insect pallet shows little preference in regard to pickiness of a particular insect. What these insects have in common, in correlation to preference is their ease of capture. The crawling insects are easy to capture they move slow but the flying insects listed above are known to hover. Because of this SWIFs are expected to have a tolerance to food shortages.
 * General Vegetation & Food Sources **

Threats and potential threats listed by Reclamation include cowbird parasitism, overgrazing, exotic species, water management, other habitat restoration efforts, fire management, and recreational impacts. Cowbird parasitism directly impacts the nesting success of the SWFL. Cowbirds lay their eggs in another birds nest and sometimes destroy some of the eggs in that nest. The nesting mother ends up adopting, hatching and raising the cowbird along with her own. The term parasitic applies when considering the distributions of resources provided by the mother aren’t fully utilized by her hatchlings. Cowbirds further consume more resources by growing at a faster rate than most birds. This in addition, gains the cowbird a physical in competing for resources in the nest. Over grazing Livestock grazing removes vegetative anchoring of sediment to slope. This contributes to higher rates of sedimentation (especially during peak flow events) and may carry along other potentially undesirable inputs to the system making it a potential threat. Exotic vegetation especially invasive ones are generally deemed for having more negative impacts then benefits. When salt cedar replaces native vegetation it is unlikely that native vegetation will be re-established in areas lost. Saltcedar increases the soil salinity as well as being a resilient competitor for water. SWFLs prefer native vegetation, especially willows but are willing to nest in saltcedar. Considering that willows are less tolerant to salinity and drought, which are expected to increase in the future, saltcedar may potentially become the next key nesting tree for SWFL. Saltcedar is difficult to classify because it currently is a threat to more favorable native alternatives but SWFL do currently nest in it. Native vegetation is more favorable to SWFL populations makes saltcedar overall a potential threat. Water management, other habitat restoration efforts, fire management, and recreational impacts may be a potential threat in the sense that the project goals may not share or consider the needs of the SWFL. Some project goals may even conflict with conditions critical to the SWFL.
 * Threats **

Reclamation installed 19 hydrostations at the head waters of Elephant Butte to monitor the impact of the Low Flow Conveyance Channel LFCC and determine if they would provide inundation of the flood plain. These stations were placed near the center of SWFL populations and were monitored once a week during their 2004-2005 breeding season. Minimum flow values were based upon how many hydrostations were flooded. Many of the stations remained flooded at 45 cfs and so 25 cfs became the minimum flow value. 18 stations were flooded when the LFCC discharged at 100 cfs and 13 flooded at 75 cfs. For a complete overbank flows of the gauged areas would need at least discharges 100 cfs.
 * Reclamation Study **

No direct correlation appeared significant between predation and parasitism to the distance from water. Nesting success had a 52% probability of occurring within 100m of surface water but did not occur past that shows a strong correlation to this distance. Within 50m of surface water, the 52% probability of occurring was very similar the 50% occurring past 50m showing little correlation to this distance away from surface water. Most of the correlations were found when comparing levels of saturation at the base of the tree. Cowbird Parasitism consistently increased as saturation increased under the nest from 8% in dry conditions to 19% in flooded conditions. Productivity consistently increases with increasing levels of saturation, yielding 2.4-2.92 fledglings.

Higher vegetation densities are considered a key component to a successful SWFL benefit significantly from. In New Mexico’s arid climate, vegetation noticeably becomes less frequent after a certain distance from the river. Dropping water levels and exposing land promoted more habitats for the SWFL and in turn contributed to SWFL population growth. Overbank flows or flushing flows were critical for washing away salt accumulation. This water decline caused overbank flows to occur less frequently which slowly lead to greater salinity and mortality of native vegetation. Willows are especially susceptible to higher soil salinity, allowing salt cedar an opportunity to get established. Temporary channels built by Reclamation and the New Mexico Interstate Stream Commission in the Butte delta were designed to connect the reservoir have created head cuts and channel incision up to the San Marcial Basin. Reclamation expects channel incision to lower the base flow along with the water table which may potentially affect the water accessibility for native vegetation.
 * SWFL Habitat Processes **

Eight SWFL territories were documented in 1995 and gradually expanded to 149 territories in 2004. Having achieved the goal of 100 territories, SWFL has been moved from the endangered list to the threatened list. Nesting areas are trending south as SWFL populations have expanded since 1995. The primary objective to creating a habitat more favorable to the SWFL involves increasing the density of native vegetation. There is an expected natural decrease in habitat diversity as the area matures. This may be a cause of increased salinity allowing saltcedar invade and impact insect populations with its less forgeable tissues. To maintain this type of habitat and prevent invasive species form taking over, overbanking flows of 100 cfs or greater would be necessary to remove salt accumulation from the gaged area. A spring pulse would prepare the area before the SWFL return from migration.

Treatment recommendations for fly catcher habitat would include carefully planned removal of saltcedar and replacing with native vegetation that yields higher SWFL nesting frequencies. Benefits would allow greater flows that could be used to help meet compact deliveries with Texas, increase channel connectivity for the RGSM, create more frequent flush flows to remove salt accumulation and allow reestablishment of native vegetation, support greater species richness in insects, most of which promote more favorable conditions for the SWFL
 * Saltcedar Management Plan **

Saltcedar patches have evapotranspiration ET rates comparable to cottonwoods and potentially higher ET rates in denser patches of saltcedar. Nagler et al. (2003) measures ET rates based on Leaf Area (m2), Canopy, and ground cover. On the basis of leaf area saltcedar had ET rates of 2.32kg/day, cottonwood estimated around 1.88kg/day and willows had the lowest at 1.52kg/day. Canopy and ground area measurements were approximately the same. Considering that willows have the lowest consumptive use make it an attractive replacement to increase stream flow. Saltcedar’s phreatophyte characteristics allow it to draw moisture, from saturated zones above the water table (FWS 2014). Its extensive root structure allows access to deeper water tables in less saturated soils. When soil moisture is more abundant saltcedar can consume great volumes of water (FWS 2014). This means that older saltcedars with a well-established root structure have the potential to lower water tables especially with increasing patch density (NMSU 2014). Saltcedar are less forgeable to most insects than native vegetation which may yield relevance to it supporting a lower diversity of insect types. This trait indirectly makes saltcedar less beneficial to the SWFL than native vegetation. Saltcedar increases soil salinity further degrading habitat for native vegetation and less forage for insects.

Removal efforts would have to consider sustainability, funding, disruption of established nesting sites and other potential impacts on the habitat. Sustainability would refer to preventing reestablishment of saltcedar. Martin T, (2001) suggests using a repeated combination of mechanical and chemical removal in order to prevent regrowth. Mechanical methods alone would likely create more root fragments that could potentially grow into many more trees. This would involve cutting the trunk and immediately applying Triclopyr herbicide for a repeated minimum of 5 years. After the tree is dead and dry, excavation tools can be used to remove the targeted tree from the vegetation area. Martin T, (2001) claims that water flow increase hours after the removal effort and 9 years later there were still no signs of saltcedar returning. The biggest hurdle for using this approach is funding. Cutting or knocking or cutting down trees over an area of this scale would be extremely costly and time consuming. Applying the herbicide over a 5 year plus would require a longer period of funding. A fair compromise if limited resources were a factor would focus on where greatest impact could be made per dollar. Denser and older stands of Saltcedar would likely yield the greatest water return. In order to avoid disturbing flycatcher populations, Restoration work could be scheduled in the time window between SWFL migration and return (August to July) confined further by a buffering time. In order to minimize disturbing flycatcher habitat, working southward from a desired starting point could continue until the nearing of nesting sites. From here procession will be timed to the southward migration of fly catcher unless restored areas become more desirable nesting areas. The water gained from vegetation removal could be used to pulse and overbanking flow to flush out the salinity. After this the area should be prepped and vegetation and further observation.

An alternative course of action would be to wait for and observe, or actually release tamarisk leaf beetles (//Diorhabda elongate//) in the Elephant Butte Headwaters and let Reclamation run another study over the area. Leaf beetles introduced to a Nevada site, in the lower Humboldt river shows that the beetles were not very effective at defoliating larger areas of saltcedar until their population expanded. Roughly 2ha were affected in 2002, 200ha by 2003 and 20000ha by 2004 (Dudley 2005). Saltcedar recovers roughly 60% of its leaves after a defoliation event (Dudley 2005). These events are based upon the generations of beetles which appear to increase with population growth and years after release. After three years of defoliation saltcedar lives but is limited to a 10% recovery (Dudley 2005). Ground water loss caused by saltcedar was reduced by 75% after the first defoliation (Dudley 2005). Reduction in canopy shading allows for new vegetation to come in (Dudley 2005). The leaf beetles serve as a food source for some birds as beetle remains appear in their fecal matter. Small mammals have been observed searching through litter for over-wintering leaf beetles (Dudley 2005). Because saltcedar can serves as a nesting structure and SWFLs aren’t picky about insect type and have a preference for insects that are easy to catch. Tamarisk leaf beetles may prove to be a beneficial addition to the food chain where balance would be better established. Non-continual studies left little to be known about the negative impacts for releasing the leaf beetle. Little studies have been completed since the release was approved in 1996, where a key study by Dudley was released in 2005 leaving little time for derived work to surface. The advantage to this initially cost effective biological solution bears resistance from speculated and unforeseeable consequence.
 * Sources **

Dudley, T. L., (2005) [|PROGRESS AND PITFALLS IN THE BIOLOGICAL CONTROL OF SALTCEDAR (TAMARISK SSP.) IN NORTH AMERICA], USDA, p.12-15

FWS ,[|Physical Methods as Part of an Integrated Management and Restoration Program: Bosque del Apache NWR, New Mexico]. U.S Fish and Wildlife Service. (Accessed 20 Feb, 2014)

Martin T, (2001) “[|A Success Story Tamerisk Control at Coachella Valley Preserve, Southern California, The Nature Conservancy Wildland Invasive Species Program].” The Nature Cnservancy Wildland Invasive Species Program.

Moore. D., (2005) “[|Status and Monitoring of Southwestern Willow Flycatchers within Elephant Butte Reservoir, New Mexico].” Bureau of Reclamation.

Nagler, P., et al. (2003). “[|Comparison of Transpiration rates among saltcedar, cottonwood and willow trees by sap flow and canopy temperature methods].” Agricultural and Forest Meteorology, **116:**73-89

<span style="font-family: 'Calibri','sans-serif'; font-size: 14.6667px;">NMSU ,[|Saltcedar Information], Weed Information, New Mexico State University, (Accessed

__ Conclusion: __ Cameron Herrington

Our findings for the San Acacia Reach proved that this portion of the Middle Rio Grande Valley is very complex and that there are many constraints placed on the system through anthropogenic and natural forcings. The river reach lies at the end of the water delivery line of the Rio Grande Compact and as such receives the last of the water once it has been utilized by the communities below the Otowi gage. While being placed at the end of the line in terms of water allocations, this reach contains some of the richest habitat for the desert willow flycatcher and the rio grande silvery minnow. We do not expect to ever see the large peak flows that were prevalent prior to the construction of Cochiti Dam, however, it would be very beneficial to the flora and fauna that inhabit the region to see more pulse flows that contain overbanking opportunities. In light of current climate change projections it is also the understanding that due to reductions in flows state-wide we can expect continued drying of the riverbed during drought conditions and must provide some form of passage for the minnow above the San Acacia Diversion Dam.

The proposed sediment control structures in the Rio Salado and the Rio Puerco would serve to provide a feasible sediment management plan to minimize the plugging of the delta region above Elephant Butte Reservoir and further aggradation of the main channel below San Marcial. This would allow river managers to tackle the issue of sediment control outside of the main channel (mostly), thus minimizing habitat disturbance of the willow flycatcher. Restoration of the main channel’s ability to meander through the valley rift would also serve to promote floodplain connectivity and would greatly benefit the riparian forest in this region.

Despite the challenges we face in regards to water availability, climate change, and other socioeconomic hurdles the San Acacia Reach has proved to be a fairly resilient portion of the Middle Rio Grande Basin. If the habitat within this river reach is expected to be preserved then we need the assistance provided by these types of engineered solutions to facilitate the maintenance of a viable ecosystem. It is our belief that cooperation between government agencies, scientists, engineers and citizens is paramount to the success of restoring this system back to a more natural existence; in doing so we also believe that the natural inhabitants will then be able to reside alongside the water delivery goals of the state. The effectiveness of restoration efforts such as those proposed herein must continually be monitored and adjusted as the system responds or once other factors that have not been accounted for become relevant.

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