EFFECT OF SPATIAL VARIABILITY IN HYDRAULIC CONDUCTIVITY ON WATER-TABLE DRAWDOWN

The field variability in saturated hydraulic conductivity and its impa ct on water table drawdown was investigated by numerically solving the Boussinesq equation for 2-D, transient waterflow between parallel dra ins. Over 500 Monte-Carlo simulations were used to carry-out a paramet ric uncertainty analysis and determine the risk of waterlogging of the crop root zone from a given drainage system. The rate of water table drawdown between the deterministic and stochastic solutions was compar ed and the growth in uncertainty in the stochastic solution with time was investigated. Results indicate that the geometric mean of K values can be used in the deterministic design of drainage systems. However; a deterministic approach using the arithmetic mean of K values may un derdesign a drainage system in contrast with the stochastic solution w hich provides a lesser water table drawdown. In general, the proposed method can be used to design drainage systems to meet a specific drawd own criteria with a specified degree of success.