Understanding changes in water availability in the Rio Grande/Rio Bravo del Norte basin under the influence of large-scale circulation indices using the Noah land surface model
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abstract
Water availability plays an important role in the socio-economic development of a region. It is however, subject to the influence of large-scale circulation indices, resulting in periodic excesses and deficits. An assessment of the degree of correlation between climate indices and water availability, and the quantification of changes with respect to major climate events is important for long-term water resources planning and management, especially in transboundary basins as it can help in conflict avoidance. In this study we first establish the correlation of the Pacific Decadal Oscillation (PDO) and El Nio-Southern Oscillation (ENSO) with gauged precipitation in the Rio Grande basin, and then quantify the changes in water availability using runoff generated from the Noah land surface model. Both spatial and temporal variations are noted, with winter and spring being most influenced by conditions in the Pacific Ocean. Negative correlation is observed at the headwaters and positive correlation across the rest of the basin. The influence of individual ENSO events, classified using four different criteria, is also examined. El Nios (La Nias) generally cause an increase (decrease) in runoff, but the pattern is not consistent; percentage change in water availability varies across events. Further, positive PDO enhances the effect of El Nio and dampens that of La Nia, but during neutral/transitioning PDO, La Nia dominates meteorological conditions. Long El Nios have more influence on water availability than short duration high intensity events. We also note that the percentage increase during El Nios significantly offsets the drought-causing effect of La Nias. Copyright 2012 by the American Geophysical Union.
