Wetlands are vital
- Created on Wednesday, 12 September 2012 19:36
Here at the headwaters of the Rio Grande, wetlands and water issues are inextricably linked by the geography and the hydrology, which together sustain the abundant biology of wetlands.
As melting snow flows out of the high country, the Rio Grande and Conejos rivers meander across the flatter Valley floor, forming wide flood plains and lush wetlands. At the same time, underlying the San Luis Valley are aquifers that have long sustained extensive wetlands, identified as marshes by early Spanish and Anglo explorers in the area. Astonishingly in this high, dry region, where the average rainfall on the Valley floor is 6-8” a year, there are over 200,000 acres of wetlands across the Valley. This is the largest concentration of wetlands in Colorado and they are also nationally and internationally important, sustaining vast numbers of migrating waterfowl and waterbirds, including the entire Rocky Mountain flock of Greater Sand Hill Cranes.
Wetlands are a valuable component of our semi-arid landscape for many reasons. They are an important aspect of the hydrology, storing water through the drier parts of the year, minimizing flood impacts, and supporting vegetation essential to both wildlife and livestock. In Colorado, only 2 to 3 percent of the landscape is either wetlands or river zones, called riparian areas. But over 75 percent of all wildlife depend upon those zones at some point in their life, including species that are either endangered or at risk. Wetlands also have a crucial role in sustaining agricultural production and they can also provide additional economic benefits and opportunities, such as recreational fishing, bird watching, duck hunting, and many more.
There is a vital water/wetlands connection wherever water is scarce. The Rio Grande and Conejos Rivers and the many smaller streams flowing into the SLV have helped to shape and influence the types of wetlands that exist here. Floodplain wetlands along the larger rivers feature backwater sloughs, oxbow lakes, and wet meadows. The vegetation communities in these areas range from tall emergent species such as softstem bulrush and cattail in semi-permanent to permanent wetlands to short emergent species such as sedges and rushes in wet meadows or seasonally flooded wetlands. Galleries of narrowleaf cottonwoods and willows also exist along rivers and creeks, ideally with understories of currant and wild rose.
Wind erosion also has played a major part in the development of wetlands throughout the SLV creating wind deflated temporary wetlands and dunes. Many of these wetlands are salt dominated with a pH of 8 or higher, promoting plant species such as inland saltgrass, blue grama, and alkali sacaton. Adjacent to these areas are uplands vegetated by rabbitbrush and greasewood shrublands.
The diversity of wetland types throughout the Valley provide important resources for a wide variety of birds and wildlife, for shelter, foraging and breeding. Complexes of wetlands situated adjacent to one another offer the greatest diversity of resources seasonally and annually. The health of wetland and riparian systems is driven by the dynamic or changing conditions both within a year and over many years. This provides some wetlands with water consistently during certain times of the year while others may only have water one in five years. Although many natural processes such as over bank flood events on the rivers and streams rarely occur now, when possible, mimicking this process with other management practices can help maintain the resources necessary to sustain many wildlife species.
When water is diverted to irrigate river corridor meadows, the wetlands function as a “sponge,” holding the water and then slowly releasing it back into the river through “return flows.” And like any sponge, water only comes out of them once they are fully wet. When the river corridor wetlands dry up due to drought or the change in historic water use patterns, there is little to no water going back into the river, making it harder to deliver water rights to those who awaited them, including the downriver states. So keeping the “sponge” wet, also keeps the habitat functioning, the ranches economically viable, and helps make the deliveries of water to downstream states, as required by the Rio Grande Compact.
The changing hydrology occurring in the Valley is making the management of irrigated meadows and wet areas more important than ever. As the areas with some of the most reliable water available, they are critical for both wildlife and agriculture. There are many management practices that can help to maintain or enhance healthy, diverse stands of forage to provide both habitat for a wide array of wildlife as well as forage for livestock. Just as soil health practices help farmers to hold water in the soil more effectively, careful grazing management can also help improve forage production and maintain enough vegetative and litter cover to minimize bare ground, capture precipitation and protect soil from erosion, fluctuating soil temperatures, helping to reduce the impacts of drought.
Also key in many of the Valley’s riparian areas is the influence of grazing on the succession and growth of cottonwoods, willows and shrubs. Cottonwoods stands along the rivers are tending more and more toward an old age class. This is due to many factors, including less flooding of wetlands in the spring, lowering of the water table, drought, disease, and grazing impacts. Currently there is very little understory of the riparian forest, which is important for birds such as turkeys and other wildlife. However, simply managing the timing and intensity of grazing can help promote new growth of young cottonwoods and willows. In some cases, excluding livestock from specific areas for a period of time can protect groves of cottonwoods and to increase understory and promote new growth. At the same time, treed areas also provide protection for livestock in harsh winter conditions and provide shade to reduce evapo-transpiration, which can increase soil moisture for grasses and shrubs.
The San Luis Valley Wetland Focus Area Committee (a collaborative group of organizations and agencies working on behalf of wetlands) held a workshop in mid-June to provide landowners and land managers a wide range of information about managing wetlands. This article draws upon the information from that program, and a handbook is being compiled from the many presentations. This free publication will be available to the public both in print and electronically. The booklet will address optimal management practices and recommendations on grazing, haying and mowing, burning, and water and weed management, as well as providing information on wildlife, land and water conservation options, and the many economic benefits of wetlands. It will also include a directory of resource organizations and agencies.
To learn more and obtain a copy of the handbook, please contact Ruth Lewis at the Natural Resources Conservation Service at 589-5661 extension 134 or the Rio Grande Headwaters Land Trust at 657-0800. The completed handbook will also be posted on line at www.riograndelandtrust.org.