| Recharge is one of the most difficult, complex, uncertain, and important hydrologic parameters to quantify in the evaluation of groundwater resources. Consequently, quantifying recharge, and its temporal and spatial variability, is one of the leading problems in hydrologic research and is important for groundwater resource evaluation, water quality protection, streamflow management, groundwater flow modeling, and contaminant transport.; Four different field-based methods, which utilize soil moisture, water level, streamflow, and baseflow data, and three modeling approaches (an analytic element model, a terrestrial biosphere model, and a soil water balance model) were used to assess the spatial and temporal distribution of natural recharge in the Trout Lake basin of northern Wisconsin for 1996–2000. The results of the different techniques exhibited similar recharge values and distributions, although each approach had its strengths, weaknesses, and limitations. The purpose of the analysis, the type of data available, and the required space and time scales should dictate the recharge method selected.; The field measurements and model simulations showed that recharge varies both spatially and temporally within the basin, enough to have implications for water resource management and ecological analyses. Temporal recharge variability is governed by the amount, timing, and type of precipitation, the soil moisture, the thickness of the unsaturated zone, the sediment type, and the land cover. For the five years assessed (1996–2000), monthly recharge rates varied from 0 to 21.3 cm/month, and annual recharge estimates varied almost three-fold. Intra-annually, recharge was limited in the basin to a few isolated events each year and exhibited a distinct seasonal pattern, with the spring snowmelt event constituting the single largest recharge event each year and minor recharge associated with spring and/or late fall rains.; Recharge also varied spatially, by as much as 18 cm per year. Spatial recharge variability is due to variability in land cover, soil type, topography, and climate. Vegetation was shown to be the strongest control on the spatial recharge distribution in this basin.*; *This dissertation is compound (contains both a paper copy and CD as part of the dissertation). The CD requires the following system applications: Adobe Acrobat; Microsoft Office. |
