Explaining streamflow variability of the Gila and Rio Grande rivers : Pacific teleconnections and catchment-scale interaction of the hydrological cycle with vegetation and soil moisture

Abstract:

The streamflows of the Gila River, N.M. and the upper Rio Grande, with headwaters in Colorado are influenced by a range of drivers including the El Nino-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation (AMO) and, for the Gila, the North American Monsoon. At the catchment scale, runoff to the river is modulated by the interaction of snowmelt, rainfall, evapotranspiration, soil moisture and vegetation. A simple eco-hydological model is used to explain the seasonal cycles of flow of the Gila (strong spring peak, weak summer peak) and upper Rio Grande (single spring peak) in terms of precipitation, snowpack, and evapotranspiration. We then examine the drivers of streamflow variability using USGS gages located upstream of human extraction, precipitation and temperature data from PRISM, and SST data from ERSST. High spring streamflow tends to occur in response to prior winter El Nino but not all high and low streamflow events can be explained by the Pacific teleconnection. Decadal variations, including low flows in the Gila and upper Rio Grande since the mid 1990s, are explained in terms of the Pacific and Atlantic Ocean decadal variability.