Diversifying the Water Portfolio for Agriculture in the Rio Grande Basin
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abstract
The Rio Grande, which extends 1,900 miles from Southern Colorado through New Mexico and Texas to the Gulf of Mexico, is the fourth longest US river and among the world's top thirty. Its lower reach forms the border between the United States and Mexico and approximately half of its watershed lays in Mexico. Snow pack feeds the upper river while summer monsoonal flow, primarily from the Rio Conchos in Mexico, feeds the lower river. The Basin is characterized by highly variable water availability that is complicated by international treaties and intrastate compacts, and water in the Basin is essentially fully allocated.The Rio Grande is one of the top 10 most endangered American and World rivers. Basin water resources, plus the societies, economies, species and ecosystems that depend on them, are seriously threatened by drought, climate change and rapid population growth. The river supplies water for over 6 million people and 2 million irrigated acres. Population growth and urban water demands are projected to double in the next 50 years. High levels of poverty and unemployment, low personal per capita income and water insecurity amongst the poorer communities exacerbate water management issues. Basin agriculture is valuable ($1 billion annually) and withdraws 80% of the freshwater resources, with the crops being grown including pecans, dairy, grass, alfalfa, vegetables, grapes, citrus, sugarcane, corn, sorghum and cotton. Climate change projections are for an increase in temperature and a decrease in net available water with the average by 2080 approaching the drought of record along with more erratic rainfall and severe storm events. Higher temperatures will result in increased potential evapotranspiration, increasing crop irrigation requirements and further stressing water supplies. The Basin is not alone in these challenges as many other arid-region river systems are facing similar crises, which provide significant water management challenges are overwhelming current practices. There is an urgent need for innovative responses to address these management challenges, with the Rio Grande being an ideal place to better understand these issues and test technology and management approaches that can better address water resource management in a changing environment.The Basin is characterized by intrastate, interstate and international relationships suggesting high visibility and critically important needs. Chronic water shortages are common and climate change projections suggest decreases in water availability, altered timing and amounts of precipitation/runoff, increasing ET and increased climate variability. During low flow years, groundwater is used to supplement water shortage situations. Aquifer stocks are declining plus there is increased intrusion of brackish water from deeper depths. This water supply situation, coupled with rapid population growth, places significant strain on water supplies and infrastructure. Combining this with a highly productive, valuable agriculture-supporting employment and income to relatively poor rural communities, there are serious consequences to not effectively managing water resources within the Basin, which is highly representative of many situations across the world with growing economies and populations. Alternative water sources, new crops and management practices and improved water conservation are all needed to sustain agricultural production, while simultaneously meeting environmental and societal needs. Despite the benefits of conserving freshwater, pursuing water supply diversification and increasing local control of water supplies, many questions remain that limit alternative water use. In particular, limited information is available on Best Management Practices (BMPs) for employing these waters for irrigation, current allocations and associated costs/benefits/risks.This project addresses the questions.........
