Hydropedological Interpretation of Regional Soil Information to Conceptualize Groundwater- Surface Water Interactions

摘要

Understanding and quantifying groundwater-surface water interactions is important for effective water resource management. Characterization of these interactions is difficult due to heterogeneities in landscapes and difficulties in measuring hydrological processes at different scales. Although soils play an integral role in the hydrological functioning of landscapes, very few groundwater-surface water interaction studies consider soils as key components of hydrologic variation. We studied 21 catchments in South Africa with available stream attributes, such as baseflow index (BFI) and hydrological variability (CVB). The soils of the catchments were interpreted and grouped into four classes based on dominant hydropedological response: Recharge, Interflow, Responsive (shallow), and Responsive (wet). The dominant soil distribution patterns in the catchments were then determined. Significant positive Spearman correlation coefficients exist between BFI and soil attributes such as depth (0.72), clay content (0.54), and the area covered by Recharge soils (0.81). The occurrence of Interflow and shallow soils is inversely correlated to BFI (-0.86 and -0.67, respectively), whereas CVB was positively correlated to the area of Interflow soils (0.81) and negatively to the area of Recharge soils (-0.75). Based on the hydropedological soil distribution pattern, three conceptual models of groundwater-surface water interactions were constructed: (i) those where vertical drainage and recharge of groundwater in the upper slopes are dominant, with return flow to soil layers in lower-lying positions, and soil and groundwater contribute to streamflow: (ii) those where vertical drainage through soils and recharge of groundwater is dominant in upper and lower lying landscape positions, there is no return flow to soils, and only groundwater contributes to streamflow; and (iii) those where lateral flow at the soil-bedrock interface is dominant throughout the catchment, limited recharge occurs, and the stream is fed through lateral flow from soils with limited contribution from groundwater.