A HYDROLOGIC BALANCE APPROACH TO SALINE SEEP REMEDIATION DESIGN

Abstract

Concern about saline seeps is increasing in the dryland production regions of Kansas and the North AmericanGreat Plains. To reclaim salt-affected seep areas, site hydrologic factors must be modified to reduce seep recharge. Asimple method is needed to help design effective remediation treatments. A hydrologic balance model, POTYLDR(Potential Yield Model, Revised), was modified and used to estimate the water balance in a saline seep recharge area andto estimate the effectiveness of various acreages of alfalfa treatments in reducing seep recharge. This model uses readilyavailable data, such as daily rainfall and temperature, NRCS runoff curve numbers, NRCS soil irrigation classes,Penman evapotranspiration parameters and Blaney-Criddle crop coefficients, to determine runoff, evapotranspiration,soil moisture, and percolation from the root zone. According to the assumed seep mechanism, deep percolation from thelocal recharge area was used to estimate seep recharge. Various percentages of the seep recharge area were shifted fromthe current wheat cropping to alfalfa to determine the reductions in total recharge and number of months contributing torecharge. A 50% reduction in total recharge required 14 to 32% alfalfa acreage depending upon site-specific factors offive targeted fields. A given alfalfa acreage reduced total recharge volume more effectively than it reduced the number ofmonths contributing to recharge. The major limitation in application of these results is selection of the percentageseepage reduction needed to provide seep control. The modeling approach provides an important indication of a systemsresponsiveness to changes in vegetation and quantifies this response in a way that is useful for designing bioremediationtreatments that require control of seepage or shallow groundwater recharge.