San Luis Valley Regional Habitat Conservation Plan Draft for Public Review
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3.0Covered Activities and ImpactsThe San Luis Valley Regional HCP will provide ESA coverage for a specific set of historical, existing, and ongoing agricultural and infrastructure activities. These covered activities and their impacts are described in detail below. Related activities that do not impact habitat for the covered species are described below under Related Activities with No Impacts. The impacts of the covered activities are summarized in Section 4, and are mitigated through the measures described in Section 5. 3.1Methods and DefinitionsMethodsThe temporary and permanent impacts that will occur in the future16 as a result of the covered activities were quantified using GIS datasets, previous documentation and reports, general industry trends, and anecdotal information about typical management practices. Whenever possible, quantitative data (e.g., length of ditches and canals, acres of pasture, length of existing floodway) were used to develop impact estimates. Specific calculation methods and assumptions for each activity are described below and in Appendix A. Considering the size of the HCP plan area and the widely dispersed nature of the covered activities, parcel-specific impact analysis is not feasible and was not conducted. A selection of geographic data that was used for the impact assumptions and analysis is shown on Figure 11. These data include the 100-year floodplain, ditches and canals, diversions, wells and gages, pasture, and priority river restoration projects, and are primarily based on the Colorado Decision Support System (CDSS) database (CDSS 2011). For each activity, a range of estimated impacts was calculated to account for variables and uncertainty. This HCP will mitigate impacts at the high end of the range to ensure that impacts are not underestimated, and will re-evaluate the covered activities, impact assumptions, and overall habitat trend every 10 years (see Section 6.2). Rotating Matrix ConceptA key dynamic influencing this HCP is the “rotating matrix” of impacts that result from most of the covered activities. The localized, small, individual impacts of each activity are scattered among hundreds of landowners and thousands of acres of habitat each year. In subsequent years, vegetation in impacted areas regenerates as other localized areas are impacted. In addition, some new habitat areas develop due to expansion and succession (Figure 10). On balance, the vast majority of the habitat remains intact and undisturbed. This pattern of impacts and regeneration has been in place for over 100 years, and will continue to occur beyond the duration of this HCP. For these reasons, many of the covered activities result in temporary impacts, and do not accumulate over time. Figure 10. Rotating Matrix Concept Figure 11. Impact Analysis Data
Impact DefinitionsTemporary, permanent, and negligible impacts are defined as follows:
3.2Routine AgricultureGrazingBackgroundWhile this activity applies mainly to cattle, it addresses the grazing of any livestock, including but not limited to cattle, horses, sheep, goats, bison, llamas, or other domesticated ungulates on irrigated and non-irrigated pasture and rangeland. Depending on their location, timing, and management, domesticated ungulates can be used as a tool to sustain riparian habitat, or can result in impacts to habitat. Detrimental impacts typically result from animals directly browsing on willows and cottonwood seedlings, or restricting riparian growth through trampling. In order to improve or maintain areas for grazing, farmers and ranchers also physically remove willow stands through cutting, pulling, grading, or prescribed fire. Many farmers and ranchers also promote willow growth in riparian areas to provide cover and calving areas. Numerous ranches in the Valley raise cattle within or adjacent to riparian habitat areas. Typically, cattle are moved to public land allotments during the summer months (June to October), and then spend the remainder of the year on the irrigated meadows in the Valley. In some cases, cattle are allowed to congregate in riparian areas in the fall and winter because of the availability of forage, cover, and water. In the spring, young calves are often reared in the shade of the riparian canopy. Many ranchers try to promote willow growth in the riparian areas while using grazing and mowing to minimize willow growth in pastures and hayfields. Since most of the early season grazing within and adjacent to riparian areas occurs in wet meadows dominated by native Baltic rush, rotational grazing techniques are less effective than they typically would be in upland pastures (Willet, pers. comm. 2005). While excessive grazing can result in the introduction of weeds, grazing is commonly used as an effective management tool to control the proliferation of weeds. It is assumed for this HCP that riparian areas where grazing has historically occurred have already been impacted and will persist in their present state unless grazing is removed from the area, or is increased.17 However, future expansions of riparian grazing could result in additional habitat impacts. Continuation of current baseline practices will not impact any additional habitat of the covered species, but will continue to prevent the regeneration of habitat in previously impacted areas. It is important to note that future declines in riparian grazing, coupled with voluntary conservation measures, such as riparian fencing programs, present an opportunity to improve riparian habitat conditions on private lands in the Valley.
General EffectsLivestock grazing can benefit or impact riparian habitat depending on the location, timing, and overall management of the animals. The New Mexico Cooperative Extension Service (Baker et al. 2001) identified several benefits of well-managed riparian grazing, including strengthened plant vigor, increased nutritional quality of autumn/winter forage, improved species composition, and increased vegetative cover. Repeated extensive summer grazing is generally considered to negatively impact riparian areas; however, winter grazing can be compatible with riparian habitat needs (Baker et al. 2001). The Recovery Plan (Service 2002a) identified livestock grazing as a potential stressor to flycatcher habitat. The Recovery Plan also describes a riparian grazing system that is compatible with a large population of flycatchers on the South Fork of the Kern River in California; an area very similar to the Valley with a low gradient, broad floodplain with perennial streamflow and a high water table, where roughly 70 percent of the flycatcher population occurs in grazed habitat. While the effects of grazing vary over the entire range of the flycatcher (Service 2002a) and the specific impacts in the Valley vary widely by parcel, riparian grazing can result in excessive use of herbaceous and woody vegetation (overgrazing) that prevents the regeneration of cottonwoods and willows. Other impacts include the reduction or elimination of willow stands, alteration of vegetation structure, streambank destabilization, erosion, and water quality impacts. Grazing has the potential to directly impact flycatcher territories, through loss or alteration of willow habitat and a reduction in new growth. These impacts could delay or prevent the regeneration of potential breeding habitat for flycatchers and cuckoos. However, in some cases, removal of willows could benefit old, decadent stands by setting back succession and promoting regeneration. Livestock can also disturb or destroy exposed nests or knock eggs or fledglings out of nests.
ImpactsThe range of potential riparian impacts due to grazing was developed by quantifying the amount of riparian habitat that is exposed to grazing, and then estimating the extent to which grazing is anticipated to expand over the next 30 years. It is assumed for this HCP that riparian areas where grazing has historically occurred have already been impacted and will persist in their present state unless grazing is removed from the area, or is increased. Riparian habitat that is exposed to livestock grazing was quantified using GIS by overlaying woody riparian habitat with pasture areas that currently support or have the potential to support grazing. (State and Federal lands were subtracted from the total area.) For this analysis, the area of overlap (1,978 acres) is the riparian habitat potentially exposed to future increases in grazing. This number was multiplied by the projected long-term changes in livestock inventories (0 to 3 percent) to determine acres of new impact resulting from expanded grazing. This impact analysis is based on the following assumptions:
Estimated Impacts:
Fence Construction and MaintenanceBackgroundFences are constructed for a variety of land management purposes. In cases where new fences cross or otherwise intersect willow stands, the willows are often removed by cutting or other methods to provide enough room for fence installation. Over time, willow stands sometimes grow along or completely cover existing fences, which need to be periodically maintained to keep them functioning properly. In these cases, the willows may be removed to provide room for fence maintenance. Most fence installation and repair that requires willow removal is conducted in the fall and winter when fields are dry and accessible. Willows typically recover within three years following fence construction or maintenance activities (Willet, pers. comm. 2005). The complete removal of willows for fence construction and maintenance does occur, but it is very infrequent and uncommon.
Elimination of willows along existing and new fence lines would result in the temporary loss of native riparian vegetation, and has the potential to directly impact riparian habitat by decreasing shrub density and fragmenting habitat patches. After fence work is completed, adjacent vegetation would regenerate within a few years of the disturbance. Considering the relative infrequency and small area of these impacts, the overall effect of fence maintenance on the covered species and their habitat is expected to be negligible. ImpactsPotential impacts of fence construction and maintenance on woody riparian habitat was not quantified for this HCP. No inventory of fences, many of which date from the early 1900s, exists within the Valley, and fence maintenance and construction occurs on an informal, ad hoc basis and is very infrequent for any given segment of fence. However, localized, short-term habitat impacts can and do occur. Therefore, the potential impacts of fence construction and maintenance are assumed to be negligible, and are mitigated within a 10-acre contingency pool for agricultural activities with negligible impacts. Ditch Clearing and MaintenanceBackgroundThe existing system of irrigation canals and ditches in the Valley has evolved for over a century into its current form. Besides serving as a critical component of the Valley’s agricultural economy, these canals and ditches have contributed to the current ground water and surface water system that supports the existing mosaic of riparian habitat. In order to ensure the delivery of water supplies and maintain the structural integrity of the ditches, ditch managers and water users periodically clear willows from their canals and ditches. There are about 606 miles of major ditches and canals in the San Luis Valley. About 335 miles of these ditches and canals are within the 100-year floodplain that contains most of the woody riparian habitat. In addition to these major ditches and canals, numerous lateral ditches serve individual fields. These lateral ditches are small and support only narrow linear bands of native woody vegetation, if any. For the purposes of this HCP, it is assumed that the smaller lateral ditches do not support a significant amount of riparian habitat that is suitable for the covered species. Therefore, the impact analysis focuses on the 335 miles of larger ditches and canals within or adjacent to the riparian corridors of the Valley. Depending on the size of the ditch and the amount of growth, most ditch clearing occurs every 5 to 10 years. Some ditch segments are cleared more frequently, while others may not require clearing for 15 to 20 years (if at all). Clearing methods may include burning, cutting, or excavating the vegetation from the main ditch channel. This may be done by hand or with light equipment (small tractors with front-end loaders or blades) for smaller ditches, while larger or more difficult ditches and canals may require heavy equipment such as backhoes and track-excavators. Many of the larger ditches and canals have adjacent access roads for ditch clearing and other maintenance purposes. Most ditch maintenance is conducted in the early spring, between winter and the start of the irrigation season (April 1), when the ground is no longer frozen and the ditches are dry. Larger projects may be conducted in the winter, as weather conditions permit. While emergency ditch maintenance may also be necessary if a ditch fails during the irrigation season (April 1 – November 1), work during this timeframe is not intended or preferred. General EffectsDitch clearing and maintenance activities typically include the removal of all willows along ditches every 5 to 10 years through burning, grubbing, and excavation. Potential direct impacts to the covered species may occur within the ditch itself and adjacent areas (for equipment access). ImpactsThe range of potential impacts due to the clearing and maintenance of ditches and canals was determined based on a range of typical ditch clearing frequencies (5 to 10 years), typical clearing widths (8 to 20 feet from the ditch edge), and the amount of riparian habitat adjacent to ditches that is likely to be impacted in a given year. Potential habitat that could be impacted includes all canals and ditches within the 100-year floodplain, and/or mapped riparian habitat.18 A total of 1,767,487 feet (335 miles) of mapped canals and ditches exist within the floodplain/habitat area. A core assumption of the HCP coverage is that the clearing of ditches occurs every 5 to 10 years, and it is randomly distributed throughout the Valley. Therefore, only a few ditches are cleared in any given year, while the others maintain their current state. The range of impacts (in habitat acres) was derived by dividing the total length of ditches by 5 (high frequency in years) and 10 (low frequency in years). The impact area was determined by multiplying the length of ditches by 20 feet (high clearing width) and 8 feet (low clearing width). This impact analysis is based on the following assumptions:
Estimated Impacts:
Water Facility Maintenance and OperationsBackgroundWater management facilities, including water wells, stream gages, and diversions, are important components of the Valley’s irrigation infrastructure. These facilities require periodic maintenance and monitoring, which may entail anything from cutting back willows to provide adequate access to removing overgrown willows and cottonwoods that may compromise the function of the facility. The ongoing maintenance of these facilities includes both minor and major maintenance activities (Vandiver 2005; 2011).
The installation of new water facilities, including headgates and gages is covered under New Water Facility Construction below. Federal activities, including those conducted by the NRCS, U.S. Army Corps of Engineers (Corps), or Bureau of Reclamation, or those requiring a Section 404 wetlands permit are not covered under this HCP. General EffectsImpacts may result from the temporary disturbance of habitat areas adjacent to existing water management facilities. Maintenance activities and access could result in the disturbance or elimination of small areas of riparian habitat. Given the extremely low level of habitat impacts that are expected to occur with each of these minor maintenance activities, and the infrequent amount of maintenance per well, gage, or diversion, the habitat impacts of minor maintenance activities are small. ImpactsPotential impacts from water facility maintenance and operations was estimated as described below based on the number of wells, gages, and diversions that are within the 100-year floodplain and/or riparian habitat. Because minor maintenance activities would have negligible impacts to habitat, the range of potential impacts in a given year was estimated based on the frequency of major disturbances to these sites under typical conditions.
Of the 457 diversions within the potential habitat area (floodplain), major maintenance or replacement is expected to occur once every 20 to 25 years, averaging about 23 per year. In total, major maintenance is expected to occur at about 69 sites per year (45 wells, 1.4 gages, and 23 diversions). The typical disturbance footprint for these major maintenance activities ranges from 200 to 10,000 square feet. This impact analysis is based on the following assumptions:
Estimated Impacts:
New Water Facility ConstructionBackgroundAs water management needs and opportunities change, new facilities (such as headgates and monitoring equipment) are periodically added to the system. The installation of these facilities, depending on their size and location, may entail new disturbance to an area and the elimination of some riparian habitat. In most cases, this construction would occur in the fall when the ditch system is not being used and the river is at its lowest level. Equipment needs vary depending on the size of the structure. Major projects require large excavators, trucks, cement trucks, and attendant vehicles, while smaller projects can be completed with smaller equipment (tractors and backhoes) but would still require some disturbance in the immediate project area. The Rio Grande Headwaters Restoration Project (SLVWCD 2001) provides recommendations for about 30 different projects with the goal of improving the sustainability and efficiency of the Rio Grande through Alamosa and Rio Grande counties (Gibson, pers. comm. 2005). General locations of the 15 high-priority projects are shown on Figure 11. An additional 25 projects are assumed to be constructed over the next 30 years, and all of these potential projects are assumed to occur within riparian habitat areas. Small impoundments, including livestock water tanks, erosion control dams, groundwater recharge pits, and other agriculture and water management-related facilities are covered if the total impoundment area has less than 20 acres in surface area, the dam is less than 10 feet high, and the total riparian/wetland habitat impact is less than 0.5 acre.19 This HCP does not cover the construction of major, regionally significant water projects such as dams, water storage, major diversions, pipelines, or other activities that are beyond what is considered typical and routine.
General EffectsConstruction of new water facilities could result in the permanent elimination of small areas of riparian habitat, and short-term elimination of habitat in temporary construction impact areas. Clearing riparian vegetation to construct small agricultural water impoundments is infrequent, and the resulting impoundment is likely to stimulate riparian vegetation growth over the long-term. For these reasons, the impacts of small impoundment construction would be negligible. ImpactsPotential impacts of new water facility construction within riparian habitat areas were estimated based on the recommendations of the Rio Grande Restoration Project report (SLVWCD 2001) and consultations with local experts. Based on those sources, a total of about 40 new facilities are anticipated, resulting in about 1.3 projects per year. The impacts from each project are expected to range between 500 and 8,000 square feet. These permanent impacts are estimated to be up to 0.2 acres per year, and will be tracked and mitigated on an on-going basis during HCP implementation. The impacts of small impoundment development will be negligible, and are mitigated within a 10-acre contingency pool for agricultural activities with negligible impacts. This impact analysis is based on the following assumptions:
Estimated Impacts:
Water Diversions, Reservoir Operations, and Flow ManagementBackgroundThe ITP will provide ESA coverage for non-federal reservoir operations, water diversions, ground water pumping, and the management of water resources in compliance with the State system of water rights administration (in effect for over a century) and the Rio Grande Compact (signed and ratified in 1938–1939). While diversions and depletions of surface or ground water may periodically dry out habitat in some locations, the redistribution of water through irrigation systems also creates habitat in other locations. The Compact and State system of water rights are both administered on a strict schedule and, by their nature, serve to ensure that the water budget will be maintained over the life of the permit, thereby helping to sustain the habitat. Water users also pump ground water wells for irrigation purposes, as regulated by the State system of water rights administration and the requirements of the Compact. Water is stored in Platoro Reservoir to be released for a variety of beneficial purposes, including helping Colorado meet its Compact obligations. The District and Applicants presume, and do not waive any argument to the contrary, that these activities (Compact administration and State law water administration activities) cannot be regulated by, and are not subject to, the ESA and its enacting rules and regulations. The Recovery Plan (Service 2002a) suggests that recovery will be operated within State water law. The purpose of this HCP is to address and permit the potential incidental take of species listed under the ESA, regardless of regulatory precedent, and to identify reasonable and proactive measures to mitigate the incidental take of those species, per the requirements of the final HCP and Implementing Agreement. General EffectsMuch of the existing mosaic of willow and riparian habitat in the Valley is dependent on the complex system of water management, delivery, and use. As some habitat areas are lost, others are gained. Water diversions and flow management could result in the short-term elimination of habitat due to drying or abandonment of some ditches and streams, or inundation of others. However, these changes in water diversions also have the potential to create or support new habitat areas. Throughout this ever-changing system, the net impact of these activities on riparian habitat is expected to be negligible. ImpactsThe potential impacts of water management activities on riparian habitat are considered to be negligible and were not quantified for this HCP. While the management of water delivery systems may result in short-term localized habitat impacts and longer-term habitat changes, these changes are not expected to result in measurable impacts to habitat. These potential impacts are mitigated within a 10-acre contingency pool for this and other agricultural activities with negligible impacts. Long-term trends and changes to habitat will be tracked as part of the HCP monitoring and adaptive management program (see Section 6). |
