Simplicity versus complexity in modelling groundwater recharge in Chalk catchments

Abstract

Models of varying complexity are available to provide estimates of recharge in headwater Chalk catchments. Some measure of how estimates vary between different models can help guide the choice of model for a particular application. This paper compares recharge estimates derived from four models employing input data at varying spatial resolutions for a Chalk headwater catchment (River Pang, UK) over a fouryear period (1992)(1993)(1994)(1995) that includes a range of climatic conditions. One model was validated against river flow data to provide a measure of their relative performance. Each model gave similar total recharge for the crucial winter recharge period when evaporation is low. However, the simple models produced relatively lower estimates of the summer and early autumn recharge due to the way in which processes governing recharge especially evaporation and infiltration are represented. The relative uniformity of land use, soil types and rainfall across headwater, drift-free Chalk catchments suggests that complex, distributed models offer limited benefits for recharge estimates at the catchment scale compared to simple models. Nonetheless, distributed models would be justified for studies where the pattern and amount of recharge need to be known in greater detail and to provide more reliable estimates of recharge during years with low rainfall.

Transient simulations of flow and transport in the Chalk unsaturated zone

“…This would suggest that all flow occurs in the matrix (Wellings, 1984). However, annual rainfall represents a summation of events of intensities ranging (Grindley, 1969) (a simple soil moisture accounting model) to derive a recharge flux from precipitation data (Rushton et al, 1989;Ragab et al, 1997;Bradford et al, 2002). Andrews et al (1997) used recharge data derived from the Penman-Grindley model as the driving flow for a simple solute transport model.…”

Parameterization and quantification of recharge in crystalline fractured bedrocks in Galicia-Costa (NW Spain)

“…In contrast, limitations of water balance models, as equivalence of shallow infiltration and recharge (Flint et al, 2002), can be easily assumed for shallow aquifers present on fractured bedrock, while strengths as spatial and temporal distributions of recharge are desirable capabilities of the modeling approach. Furthermore, where land uses and soil types are relatively uniform and limited data determines the choice of model, simple models provide a reasonable basis for long-term recharge estimates at the catchment scale compared to complex distributed models (Bradford et al, 2002).…”

Groundwater recharge in arid areas induced by tropical cyclones: lessons learned from Gonu 2007 in Sultanate of Oman

“…Estimating recharge rates in arid areas is particularly difficult, and at the same time extremely important as rainfall is scarce and infrequent. Several recharge studies have shown strong correlation between annual precipitation and the amount of recharge (Bradford et al 2002;Döll and Fiedler 2008) yielding a general perception that more rainfall will result in more recharge and consequently aquifer replenishment. Infiltration rate, however, varies with the type of soil cover, degree of initial moisture content, intensity and duration of the rainfall, depth to the water table and aquifer effective porosity, and conductivity.…”