Application of a long-term water balance of a semi-arid mountainous catchment to understand potential impacts of climate change (Invited)
Abstract
Long-term water balance investigations are needed to better understand hydrologic systems, especially semi-arid mountainous catchments. These systems exhibit considerable inter-annual variability in precipitation as well as spatial variation in snow accumulation, soils, and vegetation. Long-term studies that capture a wide range of conditions can be used to gain insight into potential future hydrologic regimes. This study used the Simultaneous Heat and Water (SHAW) model to quantify the hydrological fluxes over 24 years at the Upper Sheep Creek catchment, a 26 ha, snow-fed, semi-arid headwater drainage within the Reynolds Creek Experimental Watershed in southwestern Idaho, USA. The quantity of data afforded by the 24-year study allowed a more complete conceptual model of the system to be developed, and detailed analyses of both inter- and intra-annual flow variations. In this system, winter precipitation and spring snowmelt must first replenish the deficit within the soil water profile and ground water system before water is delivered to the stream. During this period, surface water and ground water are tightly coupled, and their interaction is critical to streamflow generation. Shortly after snow ablation however, water flux in the root zone becomes decoupled from the ground water system and subsequent precipitation does little to contribute to streamflow for the current year. Data indicated that relatively wet years characterized by drier winter and wetter spring months exhibited lower runoff ratios compared to relatively dry years with early snowmelt which exhibited higher runoff ratios. The former case appears to be due to less spatially variable precipitation due to reduced snow distribution and late-season replenishment of the soil moisture reservoir during the growing season. These dynamics suggest that projected future climate conditions characterized by stable or increased precipitation and increased rain/snow ratios may exhibit lower annual water yields due to increased evaporative fractions. This interpretation is supported by simulations of projected flow regime changes at a nearby forested watershed using downscaled GCM data, which indicate increased winter and spring evapotranspiration and declining annual hydrologic yields.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.H31I..02L
- Keywords:
-
- 1804 HYDROLOGY / Catchment;
- 1807 HYDROLOGY / Climate impacts;
- 1860 HYDROLOGY / Streamflow;
- 1876 HYDROLOGY / Water budgets