The Colorado River’s Endangered Watershed

As the megadrought continues, we are seeing the stories of falling water levels in the Colorado River, with Lake Mead and Lake Powell at 27% of capacity. Flows in the River decreased by 19% between 2000 and 2014, while climate change induced temperature increases can lead to further reduction in flow of 20% by midcentury, with higher losses possible. The Bureau of Reclamation has called on the states in the Colorado River Basin to plan to reduce water use by 15 – 30%. In California, measures are being implemented to cut back lawn watering which uses a significant amount of the water going to towns and cities and address agricultural water use through implementation of Water Management Plans. These and other measures may help but can’t be viewed as temporary. The problem goes deeper than just measuring and dividing up water from the River. Let’s consider livestock.

Grazed watershed in Capitol Reef NP. Cattle have denuded the soil, removed the vegetation and are eating the remaining shrubs due to lack of forage from a history of overuse.

Water use in California averages about 43 million acre-feet annually with agriculture consuming 80% and urban areas 20%. Agricultural water use has remained flat since the 1980’s while urban use has declined since the mid-2000’s due to reductions in outdoor water use. California’s allocation from the Colorado River is 4.4 million acre-feet annually. According to UC Davis, California irrigates about 1 million acres of alfalfa which consumes between 4 million to 5.5 million acre feet each year. Thus, growing alfalfa for livestock consumes the entirety of California’s Colorado River annual allocation. Twenty five percent or more of this hay will be exported. But let’s look further at the Colorado River Basin.

Deep gully in Capitol Reef NP caused by livestock removal of soil stabilizing vegetation. This gully exposes the adjacent soil that would have held groundwater for release downstream, but instead, the water table has fallen and storage is lost.

Colorado River water does not originate in Lake Powell or Lake Mead but comes from the mountains and its watershed which receive precipitation in the form of snow and rain. The water flows over the land and infiltrates into the ground becoming groundwater. It feeds the springs, streams, rivers, lakes, and reservoirs. It’s an integrated system of storage and supply. It has balance with runoff buffered by vegetation covering watersheds that slows its speed and erosive forces. This balance supports fish and wildlife dependent on the vegetation growing along these streams and lakes for cover and food. The vegetated areas along streams and rivers slow spring runoff, reduce erosion, and allow the water to be absorbed as groundwater which is then released slowly during the remainder of the year to feed the streams, rivers, lakes, and reservoirs instead of evaporating during the hot summer months. For example, evaporation losses from Lake Mead range from 600,000 to over 800,000 acre feet annually.

Dying stream in Grand Staircase National Monument caused by livestock removing stabilizing vegetation. A lone cottonwood is shown representing the riparian area that has been lost.

The problem with much of the Colorado River, its tributaries, and their watersheds is they lack function due to the grazing of livestock, the diversion of water into ponds and water troughs for livestock, and irrigation of pastures and hayfields. The U.S. Geological Survey has studied sites in the Colorado River Basin for decades, comparing function of watersheds grazed by livestock to those that are not grazed. These studies document watershed impairment as represented by increased sediment generation and runoff from the grazed sites. These effects result from removal of soil covering vegetation and trampling by livestock. Cattle concentrate along streams, at springs and wetlands, removing the shrubs and other stream stabilizing vegetation. Streams become incised and groundwater storage is lost. Falling water tables cause springs and wetlands to dry up. In the end, more water is lost to evaporation, groundwater storage is depleted, flow regimes are altered, and flows decline. The ecological effects of this depleted system are represented by losses in native plants, fisheries, and wildlife as well as reduced flows in the River. A recent article by noted author, George Wuerthner, discussed the impacts of livestock grazing in California. Most of the Upper and Lower Basins of the Colorado River are grazed by livestock.

The map illustrates that livestock grazing in our National Forests and Bureau of Land Management managed lands occupies the majority of the Upper Colorado River Basin and a significant portion of the Lower Colorado River Basin. The map does not show the area grazed on private or state lands, wildlife refuges and other land management categories. The map also illustrates the pervasive nature of this practice across the West, to the detriment of our water supplies, watersheds, fish, and wildlife. Streams are polluted with their waste, increasing treatment costs for our drinking water as well as those same costs for the discharge of our treated wastewater. California had a population of 5,250,000 cattle in a recent inventory. These waters, polluted with livestock waste and bacteria such as E. coli, can affect people who swim or otherwise recreate in streams and lakes.

California and the other states served by the Colorado River could help their future water supply by asking the Biden Administration to implement a livestock grazing allotment retirement program in the Colorado River Basin. The program would retire grazing allotments as the permits are up for renewal every ten years. This would yield growing benefits over time as watersheds regain function, streams and springs long dry begin to flow again, pollution costs decline, fisheries are restored, and carbon is stored to help mitigate climate change.