Water budgets are effective means to evaluate the sources and depletions of water within a basin. Both sources and depletions are being affected by human activity through climate change and human demand. Arid and semi-arid basins are particularly vulnerable to these pressures. Current and future water budgets for the Middle Rio Grande in New Mexico will be considered through applying a variety of hydrological and meteorological methods.

Results/Conclusions

Climate change will impact both the amount of runoff and the depletions of water within a catchment. Even under a scenario of little change in annual precipitation, there will be significant impacts on water supply. The Middle Rio Grande in central New Mexico in the southwestern US is an example of a snowmelt-dominated river ecosystem that is highly vulnerable to climate change. Climate warming of 2^oC is predicted to reduce montane water yield by ~10-20%, assuming no change in average annual precipitation. Major depletions along the riverine corridor are evaporation, transpiration, agricultural irrigation, groundwater recharge, and urban use. Increased urban demand and a depleting groundwater aquifer have generated a recent shift (2008) to surface water that will divert approximately 10% of average annual discharge. Other depletions such as crop use, riparian plant use, groundwater recharge, and reservoir/channel evaporation also will increase with a 2^oC temperature increase. Estimates on the extent of these changes will be presented and an overall water budget developed for the middle Rio Grande in central New Mexico under a warming scenario of 2^oC. Finally, the human and ecological implications from altered water budgets due to climate change and population demand on river and riparian ecosystems in snowmelt-dominated rivers in arid and semi-arid will be presented.