Lake Meredith Study – Partly an Example of Groundwater and Surface Water Interaction

Lake Meredith is located on the Canadian River main stem in the middle of the Texas Panhandle. It used to be the main source for water supply to 11 cities including Amarillo and Lubbock. The supply had been disrupted and/or constrained due to continuous decline of storage in the lake since 2000. Among many factors, the release from upstream Ute Reservoir in New Mexico, depletion of irrigation return flow in the Revuelto Creek Watershed, groundwater development in the catchment, and temporal variation of precipitation in the area have been identified as major factors contributing to the lake level reduction. Detailed analysis to stream flow data and precipitation data through water the budget method and comparative hydrologic method (1940-2000 vs. 2001-2006) reveals that, in general: 1) shortfall from Ute Dam release in recent years weighs 32%; 2) depletion of irrigation return flow weighs 23%; 3) effect of groundwater withdrawal weighs 22%; 4) effect of reduced precipitation from 2001 through 2006 weighs 18%; and 5) effect by all other factors including change in land-use and intrusion of salt cedar contributes a total of about 5% on the reduction. Likely scenario in this case is that lack of precipitation and increased usage triggered no release from Ute Dam in New Mexico and triggered no irrigation allotment into the watershed. Groundwater withdrawal in the catchment, especially near the lake, also leads to reduced stream flow. Reduced fresh water inflow further enhanced the salinity in the reservoir which is favorable for salt cedar intrusion. The final consequence is lower storage and high salinity in the reservoir. Declining baseflow is related to development of groundwater resources in the region. The situation may become even worse if there is no reduction in groundwater withdrawal from the Ogallala and Dockum Aquifers.