Relating Variations in Streamflow to Variations in Climate in Catchments across the Contiguous United States
Thursday, 18 December 2014
At the annual scale, water balance variability may result directly from inter-annual fluctuation of the climate drivers. However, intra-annual (i.e., within-year) variability of climate drivers and their nonlinear interactions with the landscape can also affect the inter-annual water balance variability. How climate variability at intra-annual and inter-annual time scales and hydrological effects of land use and land cover changes propagate through the landscape and result in changes in spatiotemporal variability of water balance is an important question when the earth system is facing multiple changes that challenge sustainable water management. In this study, the inter- and intra-annual variability of streamflow from over 250 natural catchments across the contiguous United States is systematically examined based on a framework that partitions the total temporal variability into inter- and intra-annual variance components. It is found that the dominance of the intra-annual variance over the inter-annual variance of streamflow decreases under drier climate, and this phenomenon is mostly controlled by the subsurface runoff. The intra-annual variance of streamflow increases with that of precipitation and decreasing with that of potential evapotranspiration. Moreover, a damping effect has been found for the temporal variance components of streamflow to those of precipitation, as indicated by the values of the deviation ratio (i.e., the variance components of streamflow divided by the corresponding components of precipitation) mostly less than one. This damping effect can be linked to the interactions of catchment water availability and evaporative energy availability at both inter- and intra-annual scales. These empirical findings will help improve water resources management at the ungauged basins and opens a window for further process-based investigations.