Optimizing Caballo Reservoir water operation by reducing evaporation losses through control of water depth and suppression of exotic plant species

In the State of New Mexico, the high demand for scarce water sources and methods assuring effective water management are of utmost importance. The requirements for effective water conservation from different types of losses in a reservoir located in an arid environment necessitate the need for research to improve water management. The types of losses include open water evaporation, vegetation evapotranspiration in the reservoir pool, evaporation from mud flats, and seepage.;This study investigated the operation of Caballo Reservoir in New Mexico to identify and minimize losses. The objectives were i) to reduce reservoir evaporation by controlling water depth and suppression of the spread of exotic saltcedar (Tamarix spp.) and other phreatophyte vegetation by drowning. The method used was a combination of evapotranspiration (ET), open water evaporation, artificial neural network (ANN) simulation, geographical information system (GIS) and reservoir optimization technique using linear programming. Latent heat flux (evaporation) was measured for 30-minute interval during 2009-2011 period at Caballo Lake Flux Tower using eddy covariance and bulk aerodynamic methods. Bulk aerodynamic method was used as check for eddy covariance method. In addition, weather data, water surface temperature and water depth were also measured for 30-minute intervals.;Weather, hydrologic and hydraulic data were used in combination with ANN, hydraulic-hydrologic modeling and reservoir linear optimization techniques to solve target problems to minimize losses. The conclusion drawn from the study are: 1) bulk aerodynamic method compared well with eddy covariance and therefore it could be used to measure evaporation of a reservoir due to its simplicity and cost; 2) ANN simulation showed that a water depth of 60.96-106.68 cm (2.0-3.5 ft) would be the best depth for minimizing evaporation loss in Caballo Reservoir; 3) the total inflow from local watersheds into Caballo Reservoir could be significant and should be considered during reservoir optimization; 4) the lake total evaporation efficiency (LTE) as a ratio of total evaporation loss and water storage volume in the Reservoir showed a better efficiency (lower LTE) as water elevation rises; 5) for submerging purposes, there was not any solution available if Caballo Reservoir monthly inflow and outflow amounts are maximum or of 3% exceedance of historical flow data. It was also not possible to recover water volume from 152,951,750.06 m3 (124,000 acre-feet) to 61,674,092.77 m3 (50,000 acre-feet) if monthly inflow from Elephant Butte Reservoir is of 5% exceedance of historical flow data; inflow is too high for the volume to decrease. But the solutions were available for any other investigated exceedance, minimum and average monthly flow values; 6) the annual amount of evaporation water loss reduced from eliminating invasive plant species by water submergence would be 7,183,167.11 m3 (5,823.4 acre-feet) while raising and keeping water at maximum elevation of 1284.88 m (4215.5 ft) in USGS NGVD29 or 1271.78 m (4172.5 ft) in United States Bureau of Reclamation (BoR) project datum.