広大な乾燥地帯を対象とした表面流・地下水流連成解析の問題点と打開策

Abstract

広域乾燥地帯において数ｋｍサイズで水平分割した場合、仮想領域の解析から表面流が1メッシュより小さな発現範囲となり、雨水が1メッシュに全て一様浸透した解析結果と等価であるとわかった。更に広域表面流・地下水流解析を安定させる打開策として、モデルを不飽和流・平面地下水流に分け、不飽和流に簡便化したDBモデルを導入し、連成解析の数値実験を試みた。その結果、過大評価となる浸透強度を除き、問題点は解決されるとわかった。

This study demonstrates a good performance of the approximate model of unsatirated flow with arranged simplification, which was originally proposed by Dagan and Bresler, in the coupling analysis of regional surface and subsurface flow in the arid area. Through a hypothetical domain divided into large meshing cells with some square kirometers, the growth range from the surface water source is limited under the arid condition. It can be shown that the maximum ramges are sonfined within a meshing cell. Several numerical tests are also conducted to confirm a validity of the solutions of groundwater heads in conjunction with surface water impacts. The successful solutions are facilely obtained with complete stability and tolerable accuracy. It can be proven that the model proposed herein is greatly helpful in hydrological coupling analysis in a regional and arid area.