ASSESSING DISTRIBUTED MOUNTAIN-BLOCK RECHARGE IN SEMIARID ENVIRONMENTS

Mountain-front recharge, including direct and indirect (or mountain-block recharge, MBR) components (Wilson and Guan, 2004), provides important water replenishment to semiarid sedimentary basin aquifers. Before water can leave the mountain block and recharge the adjacent basin it must first enter the block at the hillslope scale. Understanding how water partitions on mountain hillslopes is the first step to quantify distributed MBR. Steady-state simulations of hypothetical hillslopes support that water availability at the soil-bedrock interface and bedrock permeability are two primary controls on distributed MBR (Guan & Wilson, 2003). The ratio of precipitation (P) over potential evapotranspiration (PET) quantifies water availability (Small, 2004). In this presentation, transient simulations of hillslope water partitioning are conducted to determine a bedrock permeability threshold for significant distributed MBR in a typical mountain area of northern New Mexico. The influence of slope steepness and local climate (P/PET) are also investigated. Finally, a potential distributed MBR map for a mountain area in northern New Mexico is constructed based on a P/PET map and a slope steepness map. PET is primarily estimated from the maximum and minimum daily temperatures according to the adjusted Hargreaves equation. A newly developed geostatistic model (ASOADeK) is used to produce precipitation and temperature maps for the study area.