Altitudes of the top of model layers in the Central Valley Hydrologic Model (CVHM)

This digital dataset defines the model grid and altitudes of the top of the 10 model layers and base of the model simulated 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), which estimates dynamically integrated supply-and-demand components of irrigated agriculture as part of the simulation of surface-water and ground-water flow based on MODFLOW-2000. This application 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 an approximately 20,334 square-miles on a finite difference grid comprising 441 rows, 98 columns. Slightly less that 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 thickness of model layers is derived by sequentially subtracting the altitudes of the uppermost to the lowermost model layers. Most model layers range in thickness from 15 to more than 300 meters, and thickness generally increases with depth (Faunt, 2009). The upper 3 model layers are used to simulate the relatively shallow flow through basin-fill sediments. Layers 4 and 5 are used to represent the Corcoran Clay Member of the Tulare Formation. The lower 5 layers are used to simulate the confined deeper portion of the basin-fill sediments. 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地水流系统瞬态水文模型中所模拟的10个模型层的层顶高程，以及模型底部高程。加利福尼亚州中央谷地的总面积约为5万平方千米。中央谷地复杂的水文系统采用美国地质调查局（USGS）的数值建模代码MODFLOW-FMP（Schmid等，2006）进行模拟；该代码基于MODFLOW-2000，在模拟地表水与地下水流动的过程中，同步动态估算灌溉农业的供需综合分量。本应用在此被称为中央谷地水文模型（Central Valley Hydrologic Model，CVHM）（Faunt，2009）。借助MODFLOW-FMP，中央谷地水文模型（CVHM）以月为时间步长，模拟了1961年至2003年间中央谷地的地下水与地表水流动、灌溉农业、地面沉降及其他关键水文过程。该模型采用有限差分网格，包含441行、98列，有效模拟总面积约为20334平方英里，其中略少于50%的网格单元为有效单元。模型采用统一的水平离散分辨率，即1×1平方英里，网格方向与谷地轴线平行，为北偏西34度（Faunt，2009）。模型各层的厚度通过依次相减最上层至最下层模型层的高程计算得到。多数模型层的厚度介于15米至300余米之间，且厚度通常随深度增加而增大（Faunt，2009）。模型上层的3个层用于模拟盆地充填沉积物中的相对浅层水流。第4、5层用于表征图莱里组（Tulare Formation）的科科伦黏土层段（Corcoran Clay Member）。下层的5个层用于模拟盆地充填沉积物的承压深层区域。中央谷地水文模型（CVHM）是美国地质调查局（USGS）开发的最新中央谷地区域尺度水文模型。该模型作为美国地质调查局地下水资源计划的研究成果之一开发完成，详细信息可参见"Foreword"、A章节第iii页。