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Open-File Report 2007-1238

Open-File 2007-1238

Estimates of Monthly Ground-Water Recharge to the Yakima River Basin Aquifer System, Washington, 1960–2001, for Current Land-Use and Land-Cover Conditions

By J.J. Vaccaro, and T.D. Olsen

Conversion Factors

Inch/Pound to SI

Multiply By To obtain length
inch (in.) 25.4 millimeter (mm)
foot (ft) 0.3048 meter (m)


Monthly values of ground-water recharge, for current land-use and land-cover conditions, to the Yakima River Basin aquifer system, Washington, during water years 1960–2001 were previously estimated. Monthly estimates are spatially related to a Geographic Information System raster dataset with a grid cell size of 500 ft on a side. These estimates of monthly recharge are provided in 42 ASCII files, 1 file for each water year. The grid with its metadata and 42 files provide potential users easy access to the information.

Purpose and Scope

This report provides estimates of monthly ground-water recharge for water years 1960–2001 in an easily assessable electronic format. The estimates, from a previous study, are for current land-use and land-cover conditions (Vaccaro and Olsen, 2007). The monthly values for current conditions provide useful information for water managers, planners, and hydrologists.


Daily values of ground-water recharge to the Yakima River Basin aquifer system, Washington, were estimated and then aggregated to monthly values by Vaccaro and Olsen (2007). Daily values, in inches, were calculated by Vaccaro and Olsen (2007) using two hydrologic models for predevelopment and current land-use and land-cover conditions. Subdivisions of modeled areas, called Hydrologic Response Units (HRUs), each have a monthly value.

Refinements of the recharge values were made for nine of the larger irrigation districts with a proratable entitlement. For the 8 years (1977, 1979, 1987, 1988, 1992, 1993, 1994, and 2001) when surface-water deliveries were prorated, the amount of proration and the percentage of the prorated entitlement were used to decrease recharge for the HRUs with irrigated lands in the irrigation district. The proration percentage varied from receiving 88 percent of the entitlement in 1988 to 37 percent in 1994 and 2001, and the amount of proratable entitlement varied from 18 percent to 100 percent. Starting in 1986, recharge for the Yakima-Tieton Irrigation district was reduced by 10 percent for all HRUs with irrigated lands because the district replaced the entire distribution system with a pressurized system. During 1960-2001, the mean annual recharge was reduced by only 0.1 in. due to the refinements. For the eight proratable years, the largest reduction was for 2001 (about 1 in.) and the smallest reduction was for 1988 (about 0.2 in.).

To provide a spatially consistent means to obtain the monthly current-condition recharge values, a Geographic Information System (GIS) grid of the aquifer system was created. Each grid cell in the raster dataset is 500 ft on a side with 682,116 cells associated with a HRU. Each cell was assigned a unique identification number (ID), from 1 to 78,144, representing a HRU. Each grid cell was related to a particular HRU; the HRUs are much larger than the grid cells.

Forty-two ASCII files of monthly recharge, one for each water year, were then created. Each line of a file is related to a grid cell. Each file is 78,144 lines long and has 13 columns. The first column is the unique ID for the cell, and the remaining 12 columns are the monthly estimates of monthly recharge for the water year, starting in October (column 2) and ending in September (column 13). The monthly values for any water year easily can be brought into a GIS grid by relating the unique IDs of the grid to the ID in an ASCII file.

File Naming Conventions

Each ASCII file name starts with the letters ‘wy’, representing the words ‘water year’, that is concatenated with the last 2 digits of the water year. Each file ends with the letters ‘cur’, representing ‘current land-use and land-cover conditions’. For example, the file for water year 1960 is named ‘wy60.cur’ and the file for water year 2001 is name ‘wy01.cur’.

Distribution of Information

Listed below are two links to obtain the information. The first link is for the grid, which is named rech_id_grd. The second link is for obtaining a directory with the 42 files of monthly recharge estimates.

> Get raster grid and metadata (Files updated March, 2009)

> Get monthly files (ZIP, 35.8 MB)

Reference Cited

Vaccaro, J.J., and Olsen, T.D., 2007, Estimates of ground-water recharge to the Yakima Basin Aquifer system, Washington, for predevelopment and current land-use and land-cover conditions: U.S. Geological Survey Scientific Investigations Report 2007–5007, 30 p., accessed April 19, 2007, at

Send questions or comments about this report to the author, J.J. Vaccaro, (253) 552-1620.

For more information about USGS activities in Washington, visit the USGS USGS Washington Water Science Center home page.

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