CVHM

Criterion

Explanation

General Description

The Central Valley Hydrologic Model (CVHM) is an extensive, detailed three-dimensional (3D) computer model of the hydrologic system of the Central Valley. It is the most recent regional-scale model of the Central Valley developed by the U.S. Geological Survey (USGS). It is a tool developed in an effort to aid water managers in understanding how water moves through the aquifer system. It predicts water-supply scenarios and addresses issues related to water competition on a monthly basis from 1961-2003. CVHM simulates simultaneously changing water supply and demand across the landscape, addressing issues as:

• Conjunctive water use (interdependent use of surface water and groundwater)
• Conservation of agricultural land
• Land-use change, including environmental concerns and urbanization, and its effects on water resources
• Effects of climate change
• Subsidence

The CVHM is built on knowledge from USGS and other Federal, State, and local studies. The CVHM was constrained by comparing simulated and historically observed groundwater levels, streamflows, and subsidence. The detail and breadth of this hydrologic modeling tool provide a better understanding of valleywide hydrologic processes. This tool also provides realistic boundary conditions so that finely gridded models of smaller areas can be easily developed.

Model Domain

California's Central Valley groundwater and surface-water flow, land use, subsidence, and climate change effects.

Developer

Project Chief:  Claudia Faunt
Email:  ccfaunt@usgs.gov

Hardware computing requirements

Windows

Code language

FORTRAN

Original application

CVHM was originally developed to facilitate water management decisions for the entire Central Valley aquifer system. CVHM simulated 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 of 1x1 square mile (Faunt, 2009).

Public/proprietary and cost

CVHM is a publicly available model.

Physically or empirically based

The model is based both on empirical data and on mathematical methods.

Mathematical methods used

CVHM is a regional groundwater modeling application based on the MODFLOW-2000 computer code (USGS, 2000) and incorporates a variety of additional modules that were specifically developed to interact with MODFLOW-2000 (MF2K). A new tool for simulating the use and movement of water on the landscape, called "Farm Process", combined with the USGS MODFLOW groundwater/surface-water model to form a hydrologic model.

A comprehensive geospatial database developed using a Geographic Information System (GIS) and a texture model to characterize the hydraulic properties of the valley-fill materials. The Geographic Information System (GIS) is used to compile, manage, store, and analyze the large quantities of data in the geospatial database needed to run the model, and to understand and visualize the data output. The texture model is key to understanding how water moves through the Central Valley groundwater system. To create the model, lithologic data from approximately 8,500 drillers' logs of boreholes ranging in depth from 12 to 3,000 feet below land surface, along with other information, were compiled and analyzed.

The complex hydrologic system of the Central Valley is simulated using the USGS hydrologic modeling software, MODFLOW, combined with the Farm Process. MODFLOW-FMP simulates water movement and consumption over the landscape in agricultural, urban, and natural settings. It is designed to simulate the demand components representing crop irrigation requirements and on-farm inefficiency losses, and supplemental groundwater pumpage, canal losses and gains, surface runoff, surface-water return flows, evaporation, transpiration, and deep percolation of excess water. For the Central Valley, the tool 21 water-balance regions for water years 1962 to 2003. In order to represent the growing season adequately, the annual hydrologic cycle was divided into 12 monthly stress periods.

Input data requirements

All input data used in the model application CVHM are available at the USGS webpage describing CVHM:

Outputs

Outputs of the model application CVHM, are available at the USGS webpage describing CVHM:

Pre-processing and post-processing tools

CVHM can be coupled with Model Viewer, Model Muse, Groundwater Vistas, and Visual Modflow.

Representation of uncertainty

Uncertainty is not specified in the model description but can be assessed using sensitivity analysis.

Prevalence

Case studies of the model are described in the USGS webpage describing CVHM.

Ease of use for public entities

The webpage describing the model is specifically designed to offer an understanding of the modeling process and to easily download datasets and results:

Ease of obtaining information and availability of technical support

CVHM is well described including its functioning, scope, component modules, datasets, input and output at the address:
https://ca.water.usgs.gov/projects/central-valley/cvhm-numerical-model.html

Source code availability

The code is not available on the webpage describing CVHM. However, the contact information of the model developer is included.

Status of model development

The model is developed and available for immediate use.  Recently, this model was extended through the water year 2014 by including a scenario based on updated surface-water inflows and deliveries, updated land-use maps, and climate data (precipitation and reference evapotranspiration). Subsidence, an important consequence of intense groundwater pumpage in susceptible aquifer systems, especially in the San Joaquin Valley, is specifically simulated. In part, this extension was done to simulate the impact of land-use changes, managed aquifer recharge, and the more recent droughts on subsidence.

Challenges for integration

Obstacles for use in the Delta include lack of calibration, excessively coarse grid, and inadequate boundary conditions. See CVHM-D model description.