ZONE package of the Central Valley Hydrologic Model

This digital dataset defines the model grid, active cells in model layers 2 and 3, and geologic province arrays of the ZONE package used in the transient hydrologic model of the Central Valley flow system. The Central Valley encompasses an approximate 50,000 square-kilometer region of California. The complex hydrologic system of the Central Valley is simulated using the USGS numerical modeling code MODFLOW-FMP (Schmid and others, 2006). This simulation is referred to here as the Central Valley Hydrologic Model (CVHM) (Faunt, 2009). Utilizing MODFLOW-FMP, the CVHM simulates groundwater and surface-water flow, irrigated agriculture, land subsidence, and other key processes in the Central Valley on a monthly basis from 1961-2003. The total active modeled area is 20,334 square-miles on a finite difference grid comprising 441 rows and 98 columns. Slightly less than 50 percent of the cells are active. It has a uniform horizontal discretization of 1x1 square mile and is oriented parallel to the valley axis, 34 degrees west of north (Faunt, 2009). The ZONE Package includes the Corcoran Clay Member of the Tulare Formation, bedrock, and other geologic provinces of the 10 layers of the CVHM. In addition, the active cells in model layers 2 and 3 are identified. The CVHM is the most recent regional-scale model of the Central Valley developed by the U.S. Geological Survey (USGS). The CVHM was developed as part of the USGS Groundwater Resources Program (see "Foreword", Chapter A, page iii, for details).本数字化数据集定义了中央谷（Central Valley）水流系统瞬态水文模型中所用ZONE数据包（ZONE Package）的模型网格、第2、3层模型的激活单元及地质分区数组。中央谷位于加利福尼亚州，区域面积约5万平方千米，其复杂的水文系统采用美国地质调查局（U.S. Geological Survey，简称USGS）的数值模拟代码MODFLOW-FMP进行模拟（Schmid等，2006）。本次模拟成果被命名为中央谷水文模型（Central Valley Hydrologic Model，简称CVHM）（Faunt，2009）。该模型依托MODFLOW-FMP，以月为时间步长，模拟了1961年至2003年间中央谷的地下水与地表水流、灌溉农业、地面沉降等关键水文过程。本次模拟采用的有限差分网格包含441行、98列，有效模拟总面积达20334平方英里，其中略少于50%的网格单元处于激活状态。该网格采用统一的1×1平方英里水平离散分辨率，且与河谷轴线平行，方位角为北偏西34度（Faunt，2009）。ZONE数据包（ZONE Package）涵盖了CVHM共10层模型中的图莱里组科科伦黏土层段、基岩及其他地质分区，同时明确了模型第2、3层的激活网格单元。CVHM是美国地质调查局（USGS）针对中央谷开发的最新区域尺度水文模型，隶属于美国地质调查局地下水资源项目，详细信息可参见“前言”、A章节第iii页。