isleta

=‍‍‍‍‍‍‍Isleta Reach Restoration Project‍‍‍ = Chris Babis || **Geomorphology** Cherie Devore || **Southwestern ** Kim Fike || **Rio Grande ****Silvery Minnow ** Edward McCorkindale, MWP and MPA Candidate focusing in Hydroscience and Dispute Resolution www.unm.edu/~emccorkindale Professional Profile e: emccorkindale@unm.edu ||
 * **Hydrology**
 * Willow Flycatcher **

Hydrology of the Isleta Reach of the Rio Grande River, New Mexico
**Isleta Reach** The Isleta Reach of the Middle Rio Grande (MRG) is a 48-mile stretch that begins at the Southern boundary of the Isleta Pueblo at the Isleta Diversion Dam and extends downstream to the San Acacia Diversion near the southern boundary of the Sevilleta National Wildlife Preserve. This brief summary will provide some of the historical and prevailing hydrologic conditions. To a large degree, the cumulative effect of water management activities has severely altered the hydrologic conditions, including peak discharge. This summary will also incorporate a description of the physical and institutional constraints that presently define the system. A brief discussion will highlight suggested restoration treatments. A key component of future discussions will be to address critical habitat requirements (e.g. in-stream flows) of endangered species (e.g. Southwestern Willow Fly Catcher and Rio Grande Silvery Minnow) as defined in the 2003 Biological Opinion (BO).

Infrastructure
Although the record of human alteration and disturbance of the MRG goes back thousands of years, a more recent history is fraught with examples where humans have attempted to alter the hydrology to mitigate the risk of flooding, provide infrastructure for irrigation, procure water resources for future consumption, and recreation (Reclamation, 2009).The 20th century brought more severe alterations to the landscape comparatively, “Initially, only small channel modifications occurred, but beginning in the twentieth century, large channel-realignments, miles of levees and jetty fields, numerous diversion dams and large dams were constructed” (Massong, Makar, & Bauer, 2010, p. 4).

The Middle Rio Grande Endangered Species Collaborative Program (MRGESCP) notes the following regarding reservoirs and dams in the MRG:

(MRGESCP, 2008, p. 42) ||
 * < //The operation of numerous upstream dams (Heron, El Vado, and Abiquiu Reservoirs on the Rio Chama, Jemez Canyon Dam on the Jemez River, and Cochiti Dam on the Rio Grande) have significantly affected flows in the river by storing and releasing water in a manner that generally decreases the spring flood peaks and alters the timing of the annual hydrograph. Of the 100 greatest daily discharges since 1942 at the Central gage (08330000), all have occurred prior to the construction of Abiquiu (1963) and Cochiti (1975) Dams (USGS 2003). However, these operations have not caused significant changes in the average annual flow volumes, but seem only to affect the magnitude, timing, and duration of peak flows. According to USGS gage data, average daily flow for the Central gage for the pre-reservoir period from 1942 to 1974 was 1042.70 cfs, while average daily flow for the post reservoir period from 1975 to 2002 was 1395.75 cfs.//

To be clear, beyond infrastructure such as dams, levees, and drainage a combination of other watershed factors, such as land-use practices, institutional arrangements, soil and water conservation measures, and road construction, have also played a role in shaping the MRG. In particular, two key engineering measures have drastically impacted channel narrowing of the Isleta Reach: 1) riverside irrigation facilities constructed between the years 1918-1935; and 2) the construction of Cochiti Dam. The construction of Cochiti Dam is pertinent to the discussion involving flow regimes because “following the construction of the Cochiti dam in 1975, reduced peak discharges accelerated the encroachment of vegetation on sand bars and the evolution of sand bars into islands” ( MRGESCP<span style="font-family: Arial,Helvetica,sans-serif;">, 2008, p. 2-9). This evolution ultimately led to temporary states of accretion and island attachments to banks. Meyer (2007) describes the effect on peak discharges downstream from Cochiti:
 * <span style="font-family: Arial,Helvetica,sans-serif;">//The construction of Cochiti Dam effectively eliminated flows over 283 m3/s (10,000 cfs) (Figure 2) and in conjunction with the other tributary dams decreased the sediment load in the Middle Rio Grande by up to 80% (Lagasse, 1981). These hydrologic and sedimentologic changes accelerated the pre-Cochiti narrowing trend. Decreased flows after the initial closing of the dam tended to lock the Middle Rio Grande into a low-flow channel pattern, as channel incision was focused within the thalweg.// (Meyer, 2007, p 7) ||

<span style="font-family: Arial,Helvetica,sans-serif;">Meyer (2007) also discusses the factors driving island formation:
 * <span style="font-family: Arial,Helvetica,sans-serif;">//During 1970's, the channel configuration was controlled by the formation of river bars that quickly became stabilized by vegetation as islands (Lagasse, 1981). The decrease in sediment supply promoted channel incision, and the decreased peak flows in concert with increased low flows allowed vegetation to rapidly colonize sub-aerial surfaces within the river channel (Massong, 2003).// (Meyer, 2007, p. 8). ||

<span style="font-family: Arial,Helvetica,sans-serif;">The Isleta Diversion Dam is used to divert Rio Grande water into the Belen Highline Canal on the west side of the river in and the Peralta Main Canal on the east. Although water diversions are managed to typically occur between March 1 and October 31 each year, there is a stipulation in the legal framework that the Pueblo of Isleta may continue to request water from the Peralta Main Canal through November 15 ( MRGESCP<span style="font-family: Arial,Helvetica,sans-serif;">, 2008).

<span style="font-family: Arial,Helvetica,sans-serif;">Surface and Groundwater Hydrology
<span style="font-family: Arial,Helvetica,sans-serif;">The reduction in peak flows (peak flows are limited to 10,000 cfs from Cochiti) strays far from the recent historic flows of many western rivers, including the Rio Grande; western rivers are noted by their long-duration high flows in the spring/early summer from snow melt and lower flows throughout much of the rest of the year. For example, as cited by MRGESCP<span style="font-family: Arial,Helvetica,sans-serif;"> (2008), Scurlock (1998) documents 50 floods between the years 1849-1942, of approximately 10,000 cfs or more. According to Scurlock, floods of this magnitude occurred every 1.9 years. Despite the reduction in overall peak floods levels, monsoonal rain events have been known to impact the Isleta Reach as a result of high flows for short durations in major tributaries (e.g. Puerco and Salado). It is important to recognize the consequence of engineering the river: there has been a human-induced shift from historic flood flows and a diversity of flows to a much more controlled, regimented flow. The more historic flows like those reported by Scurlock (1998) not only defined the morphology of the river, but they were more likely conditions wherein the endemic biology adapted. These consequences have had cascading effects on riparian ecosystems, floodplain connection, groundwater hydrology, and endangered species habitat.

<span style="font-family: Arial,Helvetica,sans-serif;">The groundwater hydrology is significant in many respects, but for this summary the focus will primarily be in acknowledging the important interconnections with riparian vegetation (e.g. cottonwoods and willows) and also phenomena such as channel drying which, among other things, is a function of seepage losses to adjacent areas. One trend that has been reported on through the use of groundwater models prepared by New Mexico Interstate Stream Commission (NMISC) is that the depth to groundwater increases progressively as one moves downstream within the Isleta Reach ( MRGESCP<span style="font-family: Arial,Helvetica,sans-serif;">, 2008). The groundwater hydrology within the reach plays a role in determining the frequency of channel drying (dependent on many variables). Channel drying is an important phenomena with respect to flows, but also with respect to inundation of streambanks, especially in the summer months. Despite many points within the various sub-reaches inundating between 3000-6000-cfs, for example about 70% of the Los Lunas sub-reach inundates at 6500-cfs yet it also has the highest stretches with potential to experience channel drying (MRGESCP, 2008). Significant cumulative impacts to groundwater hydrology have also been noted by research with respect to vegetation species, composition, and structure. For example, as cited by the MRGESCP (2008), data summaries presented in a report by Crawford et al (2003) demonstrate not only a significant change in bosque area and species composition, but also a loss of salt grass meadows to the tune of approximately 20,000 acres within the reach between Bernardo and San Acacia.

<span style="font-family: Arial,Helvetica,sans-serif;">Inflows to the Isleta Reach
<span style="font-family: Arial,Helvetica,sans-serif;">Current flow recommendations through the Isleta Diversion Dam is 150 cfs during “wet-year” conditions, 100 cfs during “average” years, and all of the flow may be diverted into irrigation canals during “dry” years—an important distinction with respect to governing institutional arrangements provided global-drought-type climate change, projected increases in evapotranspiration. The Middle Rio Grande Conservancy District (MRGCD) actively manages irrigation canals and has the ability to return water back to the river through wasteways. There are two important points with respect to wasteway return flow in the Isleta Reach: 1) they are variable and depend on climate conditions; and 2) additional inflows to the river from Los Lunas wastewater treatment plant outfall (River Mile 159.5). Possible nutrient loading from agriculture and waste water treatment inflows may be important considerations for possible restoration treatment locations.

<span style="font-family: Arial,Helvetica,sans-serif;">The San Acacia Basalt intrusion has influenced the river-morphology of the Isleta Reach. The Rio Puerco and the Rio Salado join the system just upstream of the San Acacia dam and are important inflows to the system with respect to two key factors: 1) sedimentation; and 2) downstream impacts on planform evolution (e.g. channel narrowing) ( MRGESCP<span style="font-family: Arial,Helvetica,sans-serif;">, 2008). Other key surface inflows to the Isleta Reach include a network of ephemeral arroyos driven by the high-intensity, short duration monsoonal rain events in late summer; their infrequent or minimal flooding limits their sediment contribution to the MRG.

<span style="font-family: Arial,Helvetica,sans-serif;">Channel Narrowing and Bed Degradation
<span style="font-family: Arial,Helvetica,sans-serif;">A reduction in peak discharges in combination with an absence of significant spring flooding has resulted into the formation of stabilized islands, channel narrowing and accretion (MEI, 2006). Between the years 1992-2006, with low flows recorded it was demonstrated that there was an increase in bar area; between the years 2002 and 2006, all three sub-reaches within the Isleta Reach had an increase in vegetated bars and islands ( MRGESCP<span style="font-family: Arial,Helvetica,sans-serif;">, 2008).

<span style="font-family: Arial,Helvetica,sans-serif;">Understanding these channel evolution disturbance responses is further compounded by inflows, specifically episodic sediment loading from the Rio Puerco and the Rio Salado (MRGESCP, 2008). One of the primary drivers of this channel narrowing is reduction in peak discharges, more specifically bank-full discharges between 1997-2005 enabled the vegetation along channels, bars, and islands to establish and take root. Despite this narrowing within the Isleta Reach and a reduction in sedimentation by approximately 80%, the Rio Puerco and the Rio Salado still deliver high levels of fine sediment; the Rio Puerco has been ranked as one of the world’s leading sediment producing fluvial systems.

<span style="font-family: Arial,Helvetica,sans-serif;">Physical Constraints
<span style="font-family: Arial,Helvetica,sans-serif;">The cumulative effects of water management on the Rio Grande have significantly impacted the annual hydrograph, and the Isleta Reach is no exception. For example, a flood frequency analysis using 2006 data from the U.S. Army Corps of Engineers published probabilities, there is very little difference between the magnitude of a 2-year flood event and a 250-year flood event (MRGESCP, 2008). This analysis is relevant in the context of physical constraints because it illustrates the strong relationship between Cochiti Dam outflows, management operations, and dam design; this point is significant because this imposed homogeneity with respect to flows limits the diversity of the river as well as floodplain morphology (MRGESCP, 2008). Other physical constraints include irrigation infrastructure located within the Isleta Reach; significant water is removed from the system during irrigation season March-November.

<span style="font-family: Arial,Helvetica,sans-serif;">Institutional Constraints
<span style="font-family: Arial,Helvetica,sans-serif;">There are many constraints that define the hydrology of the MRG and specifically the Isleta Reach. Key institutional constraints in the reach include the Endangered Species Act of 1973, the Rio Grande Compact, in-stream flow requirements set forth by the U.S. Fish and Wildlife Service in the BO (FWS, 2003b) for the Rio Grande silvery minnow (RGSM), as well as other institutional arrangements, such as Office of the State Engineer (OSE) provisions that recognize agricultural use of surface water at the Isleta Diversion Dam, as well as other institutional arrangements that shape management actions by the MRGCD. The layered, coterminous nature of institutional arrangements in New Mexico is apparent with respect to the BO and its nested state within the Rio Grande Compact. This could be interpreted as suggestive of the institutional inertia within the system as well as the difficulty in achieving meaningful changes within the MRG. For example:
 * <span style="font-family: Arial,Helvetica,sans-serif;">//The Instream-flow requirements are also subject to provisions of the Rio Grande Compact, an interstate agreement governing the allocation of water from the Rio Grande among Colorado, New Mexico, and Texas. Articles VI and VII govern the amount of water that can be held within the States of Colorado and New Mexico, the annual volume deliverable to Texas, and how the upstream States are credited or debited their allocations.// (Bovee, Waddle, & Spears, 2008, p. 25) ||

<span style="font-family: Arial,Helvetica,sans-serif;">Restoration Treatments
<span style="font-family: Arial,Helvetica,sans-serif;">Many restoration treatments have been proposed within the Isleta Reach of the MRG. Examples of restoration treatments for the reach pivot from addressing key hydrological issues, geomorphologic changes, and more often providing habitat for endangered species. Examples include:
 * <span style="font-family: Arial,Helvetica,sans-serif;">Reach-Wide Narrowing Trend: Experimental approach with vegetation removal. Log jams as flow deflectors & habitat benefits.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Low-Flow Periods: Use drain outfalls as refugia. Determine flow requirements at different MRGCD drain outfalls.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Higher Flow Periods: Create off-channel backwater areas as nursery habitat. Focus on areas without drain outfalls or overbank inundation.

<span style="font-family: Arial,Helvetica,sans-serif;">This review of current research revealed low annual peak flows, low levels of inundation at typical or average flows, reach wide-narrowing, channel drying—among much else. Recommendations with respect to hydrology are to: 1) enhance the river connectivity of irrigation ditches and wasteways within the reach; 2) provide low-flow refugia habitat when possible; 3) focus riparian restoration measures to the lower portions of the reach where the water table is highest and where vegetation may be able to provide mosaic type habitat that supports the Southwestern willow flycatcher nesting sites near the Sevilleta National Wildlife Refuge; 4) address degraded and bare soils within the Puerco Basin to reduce sediment loading; 5) utilize bank-full stream flows when possible to move sediment through the reach; and 6) extend the hydrograph during spring snow melt to provide increased time for RGSM to return the mainstem of the river.

<span style="color: #151515; font-family: Arial,Helvetica,sans-serif; font-size: 12pt;">Isleta Reach Fluvial Geomorphology
<span style="font-family: Arial,Helvetica,sans-serif; font-size: 13px; line-height: 1.5;">Rivers play a geomorphic role in the transport of sediment and flows as changes in profile, dimension, and pattern develop to maintain a state of quasi-equilibrium in a system. These criteria are dynamic in the Rio Grande and the balance of sediment coming into the system with the sediment moving out is the central focus of maintaining dynamic equilibrium. Sediment loading beyond the carrying capacity of the river from anthropogenic changes results in an increase in sediment storage and aggradation, which is what is historically observed in the Isleta Reach of the Middle Rio Grande (MRG). Along with hydrological, climatic, and human-induced modifications to the system, changes in the river geomorphology affect the availability of habitat for the Rio Grande silvery minnow (RGSM) and the Southwestern willow flycatcher (SWFL). The connection of the river to the floodplain at various recurrence intervals and flow conditions are also important considerations for habitat suitability.

<span style="font-family: Arial,Helvetica,sans-serif;">Major changes in hydrology and sediment regimes are largely the result of man-made modifications and flood control structures established in the early to mid part of the 21st century, including Cochiti and Isleta Dams. The river dimensions and cross-sectional profile subsequently adjusted in response to historic variations in the system. A marked decrease in discharge, channel narrowing, channel incision, and the propagation of vegetated bars in the Isleta Reach contribute to current morphological conditions. A number of institutional constraints exist in concert with physical changes in the system. Water management strategies, uncertainty in water rights claims, and interstream compact demands are additional considerations for restoration and habitat initiatives.

<span style="font-family: Arial,Helvetica,sans-serif;">Summary of Historical Geomorphology
<span style="font-family: Arial,Helvetica,sans-serif;">Historically, the Rio Grande in the Isleta Reach varied from a single braided channel between Isleta and Belen (Figure 1a) to a wide braided channel between Belen and Canada Ancha around 1917 (Figure 1b). Braiding at low to moderate flows typically revealed sand bars as well as overbank flooding and avulsion <range type="comment" id="509017610_1">‍(NM OSE</range id="509017610_1">‍). The Isleta Reach system generally trended toward aggradation, which allowed the channel to shift and maintain modest sinuosity (<range type="comment" id="509017610_2">‍MRGE</range id="509017610_2">‍). A major problem for the reach, aggradation was responsible for a 7 foot (ft) bed rise from 1880 to 1924 at the Isleta Bridge as well as a 9 ft rise at San Marcial (<range type="comment" id="509017610_3">‍Harper et al, 1943</range id="509017610_3">‍). These modifications to the channel were a major impetus for sediment and flood control measures to reverse aggradation (<range type="comment" id="509017610_4">‍Mussetter</range id="509017610_4">‍).

<span style="font-family: Arial,Helvetica,sans-serif;">A notable feature in the Isleta Reach, just north of the Rio Salado, is the Socorro Uplift which was responsible for up to a 1.8 mm/year uplift rate between 1951 and 1980 (<range type="comment" id="509017610_5">‍Ouchi 1983</range id="509017610_5">‍). Though a significant geomorphological control in the past, the current modifications and changes in hydrologic regime far outweigh its effects on channel morphology.

<span style="font-family: Arial,Helvetica,sans-serif;">The topography of the floodplain and height above the channel affects the ability of the river to connect to the floodplain at a particular discharge and this is further complicated by the rate of incision experienced in the Isleta Reach. Different geomorphic processes experience different recovery rates and may require significant periods of time to recover under the influence of variable flow conditions. With this in mind, it is critical to understand past and present geomorphological relationships, current conditions, and critical areas to best address the design and evaluation of restoration strategies for the RGSM and SWFL.

<span style="font-family: Arial,Helvetica,sans-serif;">**Figure 1a.** //1917 Between Isleta and Belen.// //<span style="font-family: Arial,Helvetica,sans-serif;"> <range type="comment" id="507447656_1">‍‍‍‍‍ //

[[image:1a.jpg]]
// MEI (2002). //

<span style="font-family: Arial,Helvetica,sans-serif;">**Figure 1b.** //1917 Between Belen and Canada Ancha// //<span style="font-family: Arial,Helvetica,sans-serif;">Varying Width Single Channel Variable width braided channel. //

[[image:2a.jpg]]
//<span style="font-family: Arial,Helvetica,sans-serif; font-size: 95%;">MEI (2002). //

<span style="color: #151515; font-family: Arial,Helvetica,sans-serif;">Current Geomorphology
<span style="font-family: Arial,Helvetica,sans-serif;">Land use changes, hydrologic conditions, and anthropogenic alterations in the system have lead to major changes to the current channel in the Isleta Reach. The construction of dams and diversions designed to help with flood control and aggradation resulted in channelization of the river. Agricultural activities also contribute to changes in the flood hydrograph as well as increased sediment loads.

<span style="font-family: Arial,Helvetica,sans-serif;">In addition to channelization, the Isleta Reach has experienced drastic narrowing within the past few decades. The accretion and attachment of bars to the river bank and vegetation encroachment, coupled with long periods of drought has contributed to the channel narrowing process (MEI, 2006). Because of the marked changes in the hydrologic and sediment cycle, the floodplain has become disconnected from the river except during years of very high flow. Habitat diversity has subsequently decreased for the RGSM as a result of bar and island accretion in the system. Figure 2 illustrates the channel narrowing and island bar changes in one section of the Isleta Reach over a four-year time span (2002 to 2006).

// MRGESCP (2008). //
 * Figure 2.** //2002 vs 2006 Changes in channel planform, Isleta Reach.//

<span style="font-family: Arial,Helvetica,sans-serif;">In addition to vegetation encroachment and channel narrowing, reach-wide trends include island accretion and incision. The pattern of the river, cross-sectional geometry and its interaction and connection to the floodplain are determining factors for habitat quality for both the SWFL and RGSM. As changes to the system are made, disequilibrium can occur and change the distribution of energy along areas of habitat or refuge. Increase in width/depth ratio, and changes in slope and channel pattern can cause stream bank instability and subsequent habitat loss for the RGSM. In addition, the water surface slope and channel shape affect velocity, turbulence, and sediment transport capacity which are all important parameters in considering habitat suitability.

<span style="font-family: Arial,Helvetica,sans-serif;">A significant influence on the river sediment supply and associated geomorphology are the number of tributaries into the Rio Grande. Changes in the channel planform and the introduction of large quantities of sediment from Rio Puerco and Rio Salado have altered the river in the lower segment of the Isleta Reach. Figure 3 illustrates that the Rio Puerco is the most significant source of sediment to the Rio Grande in the Isleta Reach.

<span style="font-family: Arial,sans-serif; font-size: 12pt;"> <span style="font-family: Arial,Helvetica,sans-serif;"> //<range type="comment" id="507450446_1">‍‍‍‍Citation</range id="507450446_1">‍‍‍‍.//
 * <span style="font-family: Arial,Helvetica,sans-serif;">Figure 3. ** //<span style="font-family: Arial,Helvetica,sans-serif;">Annual Suspended Sediment. //

<span style="font-family: Arial,Helvetica,sans-serif;">Restoration treatment Options
<span style="font-family: Arial,Helvetica,sans-serif;">A combination of passive and active restoration practices is suitable for habitat restoration in the Isleta Reach. In addition to reach wide vegetation encroachment and channel narrowing, a number of habitat and restoration issues exist. During times of low flow, the lack of off-channel refugia and its subsequent disconnectivity to the main channel are not suitable for RGSM habitat. From a geomorphological perspective, habitat restoration for the minnow essentially involves redistributing the sediment mass that is stored at both bank attached bars and within mid-channel bars because they are not currently hydrologically connected.

<span style="font-family: Arial,Helvetica,sans-serif;">Geomorphological conditions should be considered under current and low flow conditions to implement river restoration activities that will create, enhance, and maintain egg retention, larval and young-of-year rearing habitat, low flow habitat, and over-wintering habitat for the RGSM. Islands, bars, and riverbanks can be modified to create slackwater features to encourage spawning.

<span style="font-family: Arial,Helvetica,sans-serif;">The Bureau of Reclamation considered a number of restoration treatments that included island/bar destabilization, creating bankline benches, removal of lateral confinements, creating bosque inundation channels, creating backwaters and embayments, and installing large woody debris (SWCA, 2008). One treatment option that would address both sediment redistribution and vegetation encroachment is island/bar modification. In addition, treated bars and islands are expected to inundate at moderate to high flows. Destabilizing vegetated bars is also expected to encourage channel widening by allowing lateral movement of the banks. Finally, channel widening will improve aquatic habitat characteristics for RGSM. Because of the low possibility of the reach to inundate under current hydrologic conditions, low flow projects using wasteways and perennial pools should also be considered for this project.

<span style="font-family: Arial,Helvetica,sans-serif;">Southwestern Willow Flycatcher
<span style="font-family: Arial,Helvetica,sans-serif; font-size: 1.1em; line-height: 1.5;">**Species background** <span style="font-family: Arial,Helvetica,sans-serif;">The Southwestern willow flycatcher (//Empidonax traillii extimus//) (SWFL) is listed as endangered according to both the federal and the State of New Mexico listings. At the time it was proposed for listing in 1993, there was a lack of information about the natural history of the species. Since then, much has been learned about the SWFL through thousands of surveys and ecological studies. These studies have provided critical information regarding nesting behavior, habitat selection and food preferences, as well as life history characteristics that have been essential for increasing SWFL populations. As of 2007, there were an estimated 280 breeding sites, which is significantly more than the 30 known breeding sites in 1995 (Durst et al, <range type="comment" id="507430554_5">‍‍‍‍‍‍‍2008‍‍‍‍‍‍‍).

<span style="font-family: Arial,Helvetica,sans-serif;">Species Characteristics
<span style="font-family: Arial,Helvetica,sans-serif;">**<range type="comment" id="507413338_6">‍‍‍‍‍‍‍‍Figure 4.**//<span style="font-family: Arial,Helvetica,sans-serif;"> Distribution of summer and wintering grounds for Willow Flycatcher species. // <span style="font-family: Arial,Helvetica,sans-serif;">//<span style="font-family: arial,helvetica,sans-serif; line-height: 1.5;">‍‍‍ // //<span style="font-family: Arial,Helvetica,sans-serif; font-size: 95%;">Sogge et al (2010). //

<span style="font-family: Arial,Helvetica,sans-serif;">The SWFL is one of four subspecies of willow flycatchers. Each subspecies has a distinct breeding range including //E. t. adastus// in the northern Rocky Mountains and Great Basin, //E. t. traillii// breeds east of the northern Rocky Mountains, //E. t. brewsteri// nests west of the Sierra Nevada and Cascade Mountains along the Pacific slope, and //E. t. extimus// breeds throughout the southwestern United States (Figure 4). Although the subspecies can look quite similar, the SWFL can be distinguished by its light or absent eye ring and slight color and morphological differences. Each species also has a unique call which is commonly used for identification purposes.

<span style="font-family: Arial,Helvetica,sans-serif;">//E. t. extimus// are typically around 15cm in length including their tail, with conspicuous light-colored wingbars. They have grayish-green back and wings, a white throat with a light gray-olive breast and a pale yellow belly. Their beak is designed for gleaning insects off foliage or for picking them out of the air. While nesting, they are strictly insectivorous and have a wide range of prey species. Fecal analysis of SWFLs from New Mexico, Arizona, and California indicates the most common prey species are bees and wasps, leafhoppers, beetles, lady bugs, dragonflies, and damselflies (Drost et al, 2001). These types of insects exhibit hovering or crawling behaviors that make them easier to catch than other invertebrate species. Because of their generalist feeding habits, it is unlikely for the SWFL to experience food shortages except in times of severe drought.

<span style="font-family: Arial,Helvetica,sans-serif;">Status of the SWFL Within the Isleta Reach, New Mexico
<span style="font-family: Arial,Helvetica,sans-serif;">The <range type="comment" id="507430554_6">‍‍‍‍‍‍‍SWFL‍‍‍‍‍‍ is viewed as an important indicator species of the health of southwestern riparian habitats (MRGESCP, 2008). The modern range of the SWLF is very similar to the historic range from west Texas to southern California, and northern Mexico to southern Colorado, Nevada, and Utah. Unfortunately, the reduction of quality and quantity of habitat has resulted in major population declines.

<span style="font-family: Arial,Helvetica,sans-serif;">The Bureau of Reclamation has completed breeding bird surveys throughout the Isleta Reach since 1999 on an irregular basis. Their surveys have been broken down into two smaller sub-reaches within the Isleta reach that were referred to as the Belen reach and the Sevilleta/LaJoya reach. The Belen reach extends from the Isleta Diversion Dam to the confluence of the Rio Puerco and the Rio Grande, which comprises about 75% of the Isleta Reach. The Sevilleta/LaJoya reach consists of the rest of the Isleta Reach from the Rio Puerco confluence to the San Acacia dam. The results of their survey are shown in the table below (Table 1). Their findings reveal some interesting trends about the nesting habits within the Isleta Reach. There were only 2 confirmed nests with 2 successful fledglings from all 36 survey sites within the Belen sub-reach from 2002-2007 (Figure 5). There was significantly more SWFL activity at the remaining 9 survey sites within Sevilleta/LaJoya sub-reach. There was a total of 13 successful nests with 33 fledglings from 2005-2007. The nests were found in four distinct groupings. The groups were identified at the confluence of the Rio Puerco and the Rio Grande, the La Joya Fish and Game Reserve, the San Juan Irrigation drain return, and in the Sevilleta Wildlife Refuge above the Rio Salado confluence. This difference in nesting concentration throughout the two sub-reaches is a strong indication of habitat preference.

<span style="font-family: Arial,Helvetica,sans-serif;">
 * Table 1. ** // Summary of bird surveys created using data from MRGESCP (2008). //

// MRGESCP (2008). //
 * Figure 5.** //Locations of SWFL nesting sites within the southern portion of the Isleta Reach.//

<span style="font-family: Arial,Helvetica,sans-serif;">Habitat Conditions for SWFL
<span style="font-family: Arial,Helvetica,sans-serif;">Vegetation characteristics for nesting habitat consists of a variety of riparian plant species. The most commonly used species for nesting substrate, according to an analysis of SWFL nests within the Middle Rio Grande, were willow species, and predominately Goodding’s willow (Moore and Ahlers, 2006). Table 2 shows the percentage of riparian vegetation species used for nesting substrate. SWFL are commonly found within thickets of native, mixed native, and exotic, or solely exotic stands of vegetation with a variable overstory of cottonwood. The exotic species include saltcedar (//Tamarix chinensis//) or Russian olive (//Elaeagnus angustifolia//). The majority of the SWFL breeding territories occur in young and mid-aged vegetation that are dominated by willow at least 10 ft high (Ahlers et al, 2002). Density of vegetation is the most common characteristic observed for flycatcher nesting preference.

<span style="font-family: Arial,Helvetica,sans-serif;">Hatten et al (2007) developed a model using GIS technology that was used to predict suitable breeding habitat for the SWFL within the Middle Rio Grande (MRG). This model divided riparian vegetation into five probability classes based upon vegetation characteristics and floodplain size. The highest density of flycatcher nests were predicted to be found within the probability Class 5. Vegetation analysis completed in 2006 and 2007 by the Middle Rio Grande Endangered Species Collaborative Program (‍‍‍‍‍‍‍MRGESCP)‍‍‍‍‍‍‍ determined and mapped the amount of Class 5 vegetation present within the Isleta Reach; the results are shown in Figure 6. Habitat probability Class 5 is shown in green. It can be observed that the highly probable nesting habitat extends throughout the northern part of the reach where SWFL surveys have remained sparse. With so much highly suitable nesting vegetation available and so few SWFLs present in the northern ¾ of the Isleta Reach, vegetation preference must not be the only environmental condition preferred by the SWFL.

<range type="comment" id="507413338_8">‍‍‍‍‍‍‍‍**Figure 6.** //Below images show Southwestern willow flycatcher habitat probability classes modeling by Hatten et al, 2007.// <span style="font-family: Arial,Helvetica,sans-serif;"> // MRGESCP (2008). //


 * Table 2.** //SWFL nesting substrate species composition. Moore & Ahlers (2006).//

<span style="font-family: Arial,Helvetica,sans-serif;">Moore and Ahlers (2006) analyze the relationship of SWFL nest placement and success for all nests found within the MRG. This study shows several important environmental conditions for nesting by SWFLs. The success of a nest, which is defined by the fledging of at least one chick, was about the same whether the flycatchers were nesting in native or exotic riparian vegetation. However, one important trend is that almost 90% of the nests analyzed were within 50 meters (m) from open water, while less than 10% were greater than 100 m from water. The greatest proportion of SWFL between 2004-2006 created their nests in habitats that were saturated throughout the entire season. There was an equal number of nests located in sites that were either flooded or dry all season. Only 2% of the nests discovered and analyzed were in habitats that were flooded early in the season and subsequently dried out. These observations can explain the absence of the SWFL from the majority of the Isleta Reach. They are present below the confluence of the Rio Puerco and the Rio Grande because this is an area with lower potential for channel drying. Inputs from La Joya Fish and Game Reserve, and the San Juan Irrigation return provide more flow presence than in northern stretches of the Rio Grande. This presence of slow moving open water is crucial for the persistence of the SWFL.

<span style="font-family: Arial,Helvetica,sans-serif;">Environmental Stressors
<span style="font-family: Arial,Helvetica,sans-serif;">Species decline is primarily a result of a variety of anthropogenic impacts. The primary driver of their declining populations is the series of impoundments and flood control mechanisms along the Rio Grande. The excessive water abstraction for agricultural and municipal uses at the Isleta Diversion Dam has resulted in regularly occurring channel drying throughout the summer months that persists longer in duration than historical drying events. This ongoing periodic lack of flow has resulted a a lower groundwater table, making the favored saturated soils of the flycatcher less available. This long stretch of dry riverbed is highly unsuitable breeding environment despite the appropriate vegetation along the floodplain.

<span style="font-family: Arial,Helvetica,sans-serif;">Wildfires are also a major threat to SWLF habitat. Floodplain drying and woody debris build-up, due to the lack of overbank flooding within the bosque, leads to greater fire risk. Prior to the installation of flood control mechanisms, such as Cochiti dam in 1975, floodplain inundation occurred more frequency and fire was not a main threat for the SWFL. A major fire can result in the complete destruction of breeding habitats and can cause significant shifts in plant community structure. A review of fire records for the Rio Grande valley from 1985-1995 showed an average of about 850 acres of bosque per year succumbed to fires (<range type="comment" id="509067412_1">‍Stuever, 1997</range id="509067412_1">‍), and it would be safe to assume that this number has increased in recent years.

<span style="font-family: Arial,Helvetica,sans-serif;">Another environmental stressor for the SWFL is the conversion of undeveloped land to urban landscapes or agricultural uses (FWS, 2002). It has also been speculated that pesticides and other types of chemicals used in agriculture can negatively affect the SWFL, however more research is needed in this area. Overgrazing practices can negatively impact SWFLhabitat in localized areas, but it is not considered a pervasive threat (<range type="comment" id="509067412_2">‍Ahlers, 1999</range id="509067412_2">‍).

<span style="font-family: Arial,Helvetica,sans-serif;">There are naturally occurring threats to //E. t. extimus// as well. Several species of birds, such as the great-tailed grackles (//Quiscalus mexicanus//), magpies (//Pica pica//), and common ravens (//Corvus corax//), prey directly on the SWFL's eggs and pose a significant threat to the survival of young SWFL. Brown-headed cowbirds (//Molothrus ater//) are brood parasites that remove the eggs of nesting birds and replace them with their own. When the SWFL returns to its nest it incubates the cowbird eggs unknowingly. These predatory and parasitic bird species bode well within urban and agricultural settings, which there is much of throughout the Isleta Reach.

<span style="font-family: Arial,Helvetica,sans-serif;">Natural history
**Figure 7.** //The Southwestern willow flycatcher is only present in its breeding habitat for about 4 months out of the year.// // MRGESCP (2008). // <span style="font-family: Arial,Helvetica,sans-serif;">The SWFL is a migratory species that over-winters in neotropical environments from southern Mexico through northern South America. They complete a 1,500-1,800 mile migration northward to their summer breeding territories in New Mexico and other southwestern states.

<span style="font-family: Arial,Helvetica,sans-serif;">The species arrives in New Mexico in early May when the Rio Grande historically had plenty of open water from spring runoff and widespread saturated soils that the species needs for its survival. The SWFLs tend to return to the same area each year, but not necessarily return to the same nest or breeding territory. Some individuals, however, have been known to shift breeding grounds to different regions and even different watersheds entirely. SWFLs begin building their nests in late May through early June and lay their eggs once the nest is completed. Their chicks hatch and fledge towards the end of July into early August. Secondary nesting attempts can be made into August if the first attempt fails. Adults and juveniles typically migrate south by the end of August or early September. //E.t. extimus// is only in its breeding habitat for about 4 months out of the year (Figure 7).

<span style="font-family: Arial,Helvetica,sans-serif;">Habitat Restoration
<span style="font-family: Arial,Helvetica,sans-serif;">In order to help expand the current populations within the Isleta Reach, the majority of habitat restoration efforts should be concentrated close to the confluence of the Rio Puerco. If significant efforts to restore habitat occur in the northern section of the reach they will most likely not be successful due to the lack of open water source. Studies have shown that //E.t. extimus// has a tendency to nest where other SWFL are already nesting. Restoration efforts are most likely to benefit the species if they are done in areas where groups of nests have already been identified rather than several miles away. The creation of willow swales would provide essential habitat if site selection is appropriate. According to the MRGESCP (2008), appropriate swale construction should be within one mile of other known territories, but no closer than 1/4 mile to existing territories. They should be adjacent to the active river channel and have a low depth to groundwater. The swales should also be constructed away from any recreation areas such as picnic areas and have a wide buffer between the restoration area and the levee. The minimum recommended size for the swale is 5 acres.

<span style="font-family: Arial,Helvetica,sans-serif;">Other restoration efforts should include the preservation of existing nesting grounds and any attempts to maintain flow would improve the available habitat throughout the reach.

<span style="font-family: Arial,Helvetica,sans-serif;">Rio Grande Silvery Minnow
<span style="font-family: Arial,Helvetica,sans-serif; font-size: 1.1em; line-height: 1.5;">**Rio Grande Silvery Minnow Characteristics**

__<span style="font-family: Arial,Helvetica,sans-serif;">History of the Rio Grande Silvery Minnow in the Middle Rio Grande River, and the Isleta Reach __
<span style="font-family: Arial,Helvetica,sans-serif;">At one time, the Rio Grande silvery minnow (//Hybognathus amarus//) (RGSM) ranged from the Gulf of Mexico upstream to Española, New Mexico, and up the Rio Chama past Abiquiu, New Mexico (Bestgen & Platania, 1991, as cited by MRGESCP, 2008). Currently, RGSM inhabit about 5% of this historical range, within the portion of the Rio Grande between Angostura Diversion Dam (Sandoval County, New Mexico) and the delta of Elephant Butte Reservoir (Sierra County, New Mexico) (MRGESCP, 2008). In 1994, the RGSM became a federally listed endangered species; in 1996 it was listed as endangered by the state of New Mexico. Since 1993, RGSM sampling has taken place in the Middle Rio Grande (MRG), with 6 monitoring sites in the Isleta Reach. Between 2005 and 2007 (the last three years that RGSM survey data are publicly available through MRGESCP, []), monitoring data indicated that RGSM in the reach are strongly affected by drought and channel drying. When the Isleta Reach is compared to the Albuquerque Reach (upstream) and San Acacia Reach (downstream), one observes that high flows can displace many RGSM downstream into the Isleta and San Acacia Reaches due to channelization. Increased populations upstream from stocking and transplanting, due to the need for fish rescues in drying segments of the river, may affect the numbers of RGSM that are caught during monitoring (MRGESCP, 2008).

__<span style="font-family: Arial,Helvetica,sans-serif;">Rio Grande Silvery Minnow Life History __
RGSM spawning and recruitment rates are coupled with spring snowmelt runoff flows, which peak between April and June (MRGESCP, 2008). After eggs are expulsed and fertilized, they may either settle in low-velocity areas, or become suspended in more turbulent flows and drift downstream. Eggs hatch within 1 - 3 days, and larvae develop the ability to swim within the next 1 - 2 days (Platania, 1995, as cited by MRGESCP, 2004). Within 50 days, the fish reaches itsjuvenile stage, and then is an adult within the first year (Dudley & Platania, 1997, as cited by MRGESCP, 2004). Although algae is more important for early life stages of RGSM, the fish also generally feeds on diatoms, larval insect skins, and decayed plant material in bottom sediments (Sublette et al, 1990, as cited by MRGESCP, 2004). Medley & Shirey (2013) notes that RGSM have not been observed to make upstream migrations, indicating that RGSM would be stable in population location, and that the downstream drift of fish and eggs that is currently observed in the Rio Grande is due to anthropogenic changes to the river system, and associated environmental stressors.

__<span style="font-family: Arial,Helvetica,sans-serif;">Environmental Stressors of the Rio Grande Silvery Minnow __
<span style="font-family: Arial,Helvetica,sans-serif;">When the RGSM was federally listed in 1994, FWS stated that population declines are attributed to dewatering, channelization, regulation of flow, diminished water quality, and competition with or predation by non-native species (FWS, 1994). In 2003, FWS defined critical habitat for RGSM, within which there are biological and physical features that are essential to the fish's conservation and that may require special management and protection (FWS, 2003a). In the same year, FWS issued a Biological Opinion (BO) regarding the effects of Bureau of Reclamation (Reclamation) river operations, U.S. Army Corps of Engineers (Corps) flood control operations, and other non-federal agency actions on the RGSM and Southwester willow flycatcher (SWFL) (FWS, 2003b). The BO concluded that water and river operations in the MRG, as proposed in the 2003 Biological Assessment (BA), are likely to jeopardize the continued existence of RGSM and SWFL, and adversely change habitat that is critical for RGSM. These operations have created a number of environmental stressors for the RGSM (Table 3) that complicate current and future recovery actions.


 * Table 3.** //River and water operations in the Middle Rio Grande have created a number of environmental stressors for the Rio Grande silvery minnow that complicate current and future recovery actions.//

__<span style="font-family: Arial,Helvetica,sans-serif;">Habitat Relationships __
<span style="font-family: Arial,Helvetica,sans-serif;">FWS defined critical habitat for RGSM in the MRG to be between Cochiti Dam to the utility line crossing the Rio Grande in Socorro County (Table 4), a total length of 157 miles. Portions of this area that fall within Isleta Pueblo lands are specifically excluded from FWS's definition (MRGESCP, 2004).


 * Table 4.** //U.S. Fish and Wildlife Service defined critical habitat for RGSM in the MRG in 2003. Critical habitat is composed of four primary elements. (FWS, 2003a,b, as cited by MRGESCP, 2004).//

and so on...

<span style="font-family: Arial,Helvetica,sans-serif;">Rio Grande Silvery Minnow Habitat Conditions in the Isleta Reach

 * ====__<span style="font-family: Arial,Helvetica,sans-serif;">Fish Movement __====

The U.S. Geological Survey (USGS) has installed three stream gages in the Isleta Reach above San Acacia Diversion Dam. Focusing on macrohabitat conditions for RGSM, Figures 8, 9, and 10 show annual averages of discharge at these gages.

// Annual discharge statistics from USGS, 2014. National Water Information System: Web Interface. [Online] Available at: http://waterdata.usgs.gov/nwis. //
 * Figure 8. ** // USGS gage 08331160, Rio Grande near Bosque Farms, NM - 6-year mean flow (cfs). //

The RGSM spawning period is between April and June (day 75 and 151 of the year) (MRGESCP, 2008). Figure 8 indicates that 6 or 7 year average at U.S. Geologial Survey (USGS) gage # 08331160 has increased spring flows in late April through late early July.

// Annual discharge statistics from USGS, 2014. National Water Information System: Web Interface. [Online] Available at: http://waterdata.usgs.gov/nwis. //
 * Figure 9.** //USGS gage 08331510, Rio Grande at Sate Highway 346 near Bosque, NM - 7-year mean flow (cfs).//

At USGS gage # 08331510, the 7-year average discharge is similar, with increased discharge in late-April through early-July (Figure 9). Compared to gage # 08331160, flows are about 150 cfs lower.

// USGS gage 08332010, Rio Grande Floowdway near Bernardo, NM - mean flow (cfs). // // Annual discharge statistics from USGS, 2014. National Water Information System: Web Interface. [Online] Available at: http://waterdata.usgs.gov/nwis. //
 * Figure 10. **

The period of record at gage # 08332010 is longer than the other gages in the reach (Figure 10). The 34-, 15-, and 5-year averages show that the amount of water flowing through this gage is decreasing, and that spring flows may be increasing earlier in the year. In the last 5 years, flows at this gage have averaged at or near 0 cfs, intermittently, between Day 201 and 301 (late-August to late-November). This may indicate river drying in the area of this gage, or lower flows, that negatively impact the longitudinal connectivity (i.e. fish and eggs successfully travelling downstream) and lateral connectivity (i.e. availability of instream, side channel, and floodplain RGSM habitat) of the Isleta Reach. || ====__<span style="font-family: Arial,Helvetica,sans-serif;">Longitudinal Connectivity __==== <span style="font-family: Arial,Helvetica,sans-serif; line-height: 1.5;">The upstream and downstream extents of the Isleta Reach are defined by the Isleta Diversion and San Acacia Diversion Dams (respectively), inhibiting longitudinal connectivity of the Rio Grande. RGSM eggs have been observed throughout the river to drift downstream more than 150 km, but can also settle in low-velocity areas near spawning sites (Medley & Shirey, 2013). Portions of the Isleta Reach are prone to drying during heavy water withdrawals and dry years, limiting longitudinal connectivity further. In particular, MRGESCP (2008) identifies increased drying potential beginning between River Miles (RM) 159 and 160, extending downstream at least as far as RM 153 (Figure 11). The 10-mile segment between the Isleta Diversion Dam, where drying potential is low, and RM 160, leaves little distance for RGSM to spawn and for eggs to drift downstream and entrain in low-velocity habitats. Even as the potential for drying decreases within the 37 miles between RM 151 and the San Acacia Diversion Dam, the channelization of the river can cause RGSM and eggs to flush downstream, without an opportunity to rest or settle in low-velocity areas (MRGESCP, 2008).

//<span style="font-family: Arial,Helvetica,sans-serif; font-size: 13px; line-height: 1.5;">Adapted from MRGESCP (2008) (Exhibits 2-12, 2-13, 2-14). // ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 13px; line-height: 1.5;">Figure 11. **//<span style="font-family: Arial,Helvetica,sans-serif; font-size: 13px; line-height: 1.5;">Propensity for Channel Drying in the Isleta Reach, New Mexico. //

<span style="font-family: Arial,Helvetica,sans-serif; line-height: 1.5;">MRGESCP (2008) notes that, prior to significant human alteration in the 14th century, the Rio Grande floodplain was wide and shallow, with many large sand bars and a braided appearance at low to moderate flows. At that time, the river experienced extensive overbank flooding, and abrupt shifting of the channel. In the current system, limited overbanking into the floodplain may provide the only habitat that is available for RGSM. Figure 12 shows areas that potentially overbank at specific flows in the Rio Grande. Considering the discharges that have been observed at the ages in the reach (Figures 8, 9, 10), and their location within the reach (RM 164, RM 141, and RM 131, respectively) indicate that there is little overbanking. Figure 12 indicates that overbanking is expected to occur at 3,000 cfs between RM 166 and 165, RM 147 and 145, and RM 144 and 143. The mean flows since at least 1970 indicate that flows do not regularly exceed this amount through the Isleta Reach. Therefore, RGSM habitat, in most years, is limited to the main channel or directly adjacent to it.
 * ====__<span style="font-family: Arial,Helvetica,sans-serif;">Lateral Connectivity __====

//<span style="font-family: Arial,Helvetica,sans-serif;">Adapted from MRGESCP (2008) (Exhibits 4-5, 4-6, 4-7). // || ====__<span style="font-family: Arial,Helvetica,sans-serif;">Overall Habitat __====
 * <span style="font-family: Arial,Helvetica,sans-serif; line-height: 1.5;">Figure 12. ** //<span style="font-family: Arial,Helvetica,sans-serif; line-height: 1.5;">Overbank Flooding in the Isleta Reach, New Mexico. //

<span style="font-family: Arial,Helvetica,sans-serif;">Habitat Restoration for the Rio Grande Silvery Minnow
__<span style="font-family: Arial,Helvetica,sans-serif; font-size: 1.06em;">Restoration Goals for RGSM __ <span style="font-family: Arial,Helvetica,sans-serif;">The 2003 FWS Biological Opinion (BO) describes Reasonable and Prudent Alternatives (RPAs) to avoid the likelihood of jeopardizing RGSM and SWFL, an d of adversely affecting RGSM habitat (FWS, 2003b).

__<span style="font-family: Arial,Helvetica,sans-serif;">Opportunities for RGSM __
Sampling of RGSM distributions in the MRG indicate that there is a need to maintain base flows in the Rio Grande in order to prevent river drying, particularly in the Isleta Reach. During periods of drought, when river drying is most likely, watered refuge habitat can maintain RGSM in the reach without the need for rescue and relocation (MRGESCP, 2008). When flows are higher and they inundate floodplain areas, the descending limb of the hydrograph following peak flows may provide a greater opportunity for RGSM to return to the main channel, if the hydrograph is extended.

<span style="font-family: Arial,Helvetica,sans-serif;">Discussion//Caveats
<span style="font-family: Arial,Helvetica,sans-serif;">There are a number of factors, outside the scope of habitat restoration, that prevent the complete restoration of the Rio Grande to conditions that were present before Spanish imperialist occupation, or even before construction of Cochiti Dam (the northernmost extent of critical habitat for RGSM). In the current Rio Grande system, full habitat restoration is complicated by the extinction of several native aquatic species, as well as development of current technical/engineered, economic, and legal systems in the historic floodplain (MRGESCP, 2004). Further, all observations and studies of RGSM life history and ecology have taken place within current conditions and it's contemporary range. Since the current conditions of RGSM are complicated by anthropogenic development of the floodplain, these observations can lead to a misunderstanding of the RGSM's real habitat preferences and needs (MRGESCP, 2004). Further, low population density and patchy distribution, and a small number of sampling sites, prevent reliable estimates of the RGSM's current population (MRGESCP, 2004). ||

<span style="font-family: Arial,Helvetica,sans-serif;">References

 * <span style="font-family: Arial,Helvetica,sans-serif;">Ahlers, D., Solohub, C., Best, E., & Sechrist, J., 2002. //2001 Southwestern willow flycatcher survey results: selected sites along the Rio Grande from Velarde, New Mexico, to the headwaters of Elephant Butte Reservoir//. Bureau of Reclamation, Denver, CO.
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