Application of HEC-HMS 3.4 in estimating streamflow of the Rio Grande under impacts of climate change

The Rio Grande originates from the San Juan Mountains of southern Colorado, and flows year-round south through the entire length of New Mexico. It has an approximate drainage area of 1.9 million acres in New Mexico (USGS 1996), and provides habitat for diverse wildlife along the river, including the silvery minnow, an endangered indicator species. The hydrology of the river is characterized by low flow during the winter months, a snow-induced peak in spring/early summer, and smaller peaks in July and August due to the effect of the monsoon season. In the five recent decades, the Rio Grande has experienced near averages as well as extremes similar to the variability of the climate of the last one-thousand years (Papadopulos 2004). Moreover, many climatic models have generated future climate change scenarios associated with altered temperature and precipitation. To estimate future average streamflow of the Rio Grande, the Hydrologic Engineering Center – Hydrologic Modeling System (HEC-HMS) software was adopted to simulate streamflow for different climate change scenarios for the Rio Grande watershed above Elephant Butte Dam. The historical monthly streamflow, precipitation, and temperature of the tributary areas for the Rio Grande from Del Norte, Colorado, to Elephant Butte, New Mexico were collected to calibrate an HEC-HMS hydrologic model for the period of 1971-2000. With the projection for temperature and precipitation associated with future climate change scenarios generated by a climatic General Circulation Model (GCM), the calibrated hydrologic model for the Rio Grande was employed to generate six future climate change hydrographs. The results generated by the calibrated hydrologic model represent the amount of water New Mexico delivers to Texas. The projection of the streamflow under different scenarios of climate change at Elephant Butte outlet were used in conjuction with the projection for the Rio Grande at Otowi bridge to quantify how well New Mexico would meet its obligations to deliver water to Texas under the requirements of the Rio Grande Compact. A range of modeled streamflow projected total annual volume drops at Elephant Butte from 8.5% to 54.5% as well as one-month earlier arrival of spring induced runoff, resulting in New Mexico straining to meet delivery obligations.Civil EngineeringMastersUniversity of New Mexico. Dept. of Civil EngineeringCoonrod, JulieStone, MarkThomson, Bruc