GroMoPo Metadata for West-Central New Jersey USGS model

This study was undertaken to characterize ground- water flow in the Stony Brook, Beden Brook, and Jacobs Creek drainage basins in west-central New Jersey. The 89-square-mile study area is underlain by dipping beds of fractured siltstone, shale, and sandstone and by massive diabase sills. In all of the rocks, the density of interconnected fractures decreases with depth. A major fault extends through the study area, and rocks on both sides of the fault are extensively fractured. The average annual rates of precipitation and ground-water recharge in the study area are 45.07 inches and 8.58 inches, respectively. The rate of recharge to diabase rocks is about one-half the rate of recharge to other rocks. Part of the surface runoff from diabase rocks enters the ground-water system where it encounters more permeable rocks. Most ground water in the study area follows short, shallow flow paths. A three- dimensional finite-difference model of ground-water flow was developed to test hypotheses concerning geologic features that control ground-water flow in the study area. The decrease in the density of interconnected fractures with depth was represented by dividing the model into two layers with different hydraulic conductivity. The pinching out of water- bearing beds in the dip direction at land surface and at depth was simulated as a lower hydraulic conductivity in the dip direction than in the strike direction. This model can be used to analyze ground-water flow if the area of interest is more than about 0.5 square mile.本研究旨在表征新泽西州中西部斯通尼溪（Stony Brook）、贝登溪（Beden Brook）与雅各布斯溪（Jacobs Creek）流域的地下水流动（groundwater flow）特征。本次研究区面积为89平方英里，下伏倾斜裂隙粉砂岩、页岩、砂岩以及块状辉绿岩床。所有岩体中的连通裂隙密度均随深度增加而降低。一条大型断层贯穿研究区，断层两侧的岩体均发生了强烈的裂隙化作用。研究区年均降水量与地下水补给量分别为45.07英寸与8.58英寸；辉绿岩岩体的地下水补给速率约为其他岩体的一半。辉绿岩区域产生的部分地表径流会进入地下水系统，并在此遇到渗透性更强的岩体。研究区内的多数地下水均沿短浅的流动路径运移。本研究构建了三维有限差分数值模型（three-dimensional finite-difference model），用以检验调控研究区地下水流动的地质特征相关假说。模型通过划分为两层并设置不同渗透系数（hydraulic conductivity），来表征连通裂隙密度随深度降低的特征。针对地表与深部沿倾向方向含水层的尖灭现象，模型将其模拟为倾向方向的渗透系数低于走向方向。该模型可用于分析面积不小于约0.5平方英里的区域的地下水流动情况。