An integrated conceptual and modeling framework for studying groundwater recharge in arid and semi-arid regions

摘要

Rapid population growth in arid/semi-arid regions like the southwestern U.S. is increasing the demand and reliance on groundwater resources each year. These resources are limited and require reliable long-term management plans to ensure sustainability. Basin scale groundwater models are typically developed and used as the primary tool supporting management plans. Successful long-term plans depend heavily on specifying realistic rates of recharge to the saturated zone. Typical groundwater models for basins in more arid environments however, generally over-simplify recharge. In most cases this is inappropriate because recharge is complex, depends on many factors, and exhibits pronounced spatial and temporal variability within a basin. Two key steps are proposed to obtain more accurate recharge estimates. First, important sub-regional scale recharge mechanisms within the basin need to be identified. Second, important surface and subsurface hydrologic processes associated with these mechanisms must be evaluated and better understood. Physically based, integrated hydrologic codes are available and capable of simultaneously simulating surface and subsurface processes. A conceptual and modeling framework is developed based on a physically based integrated hydrologic code and GIS techniques to study recharge in semi-arid/arid basins. Within this framework, a step-wise approach is taken to identify, conceptualize and numerically analyze different relevant 'hydro-geomorphic' recharge mechanisms. This is an important step in developing a successful fully integrated hydrologic model for the basin flow system. The Black Mesa basin flow system in northeastern Arizona is used to demonstrate the proposed framework.