Definition: Water usage represents the amount of water that was reported used each calendar year by water right holders. All water right holders are required by state law to complete and return a water use report, whether any water was used or not, to the Kansas Department of Agriculture, Division of Water Resources (KDA-DWR). The State of Kansas is the only western state among those that follow the water appropriation doctrine (first in time, first in right) that has a mandatory state-wide water reporting program. The KDA-DWR has archived water use data since 1958; however, only since 1987 has the agency had the regulatory authority to enforce the mandatory reporting. Since that time, the KDA-DWR generally has a 99 percent return rate on water use reports. In 1988, KWA-DWR, in conjunction with the Kansas Water Office, initiated a program to identify and correct potential inconsistencies on the reports. When an inconsistency is found, the water right holder is contacted to further clarify the water use report.

Relevance to understanding water resources: Water use reports are the primary data set used to produce an estimate of the total amount of water used and to analyze a variety of water use conditions each year. Because each water use report is referenced to the actual groundwater well or surface water pump that diverted the water, the amount of water used can be spatially quantified and then compared to other spatial features, such as changes in groundwater elevations, streamflows, or precipitation.

Discussion: The water usage graph shows the total amount of ground water reported used by water rights within the High Plains aquifer in comparison with the seasonal precipitation from 1990 to 1998. For water rights within the Kansas High Plains aquifer region, groundwater consistently accounts for approximately 99 percent of the total reported use, and the average fraction of groundwater used for irrigation is approximately 95 percent of the total. The graph also shows the inverse relationship between water use and seasonal precipitation that occurs between the months of March to October. As would be expected, when more precipitation occurs during the growing season, the need for supplemental water use, primarily irrigation, decreases.

Data Sources and Methods: The reported water use information was obtained from the KDA-DWR Water Rights Information System for each year between 1990 and 1998, and represents only appropriated or vested water rights. The total amount of water reported used was summarized for all uses (irrigation, municipal, recreation, etc.) and sources (ground or surface water). Note that 1999 water use reports will not have been processed through the quality control program until almost the start of the 2001 calendar year.

Seasonal precipitation data was retrieved from the Hydrodata software of Hydrosphere Data Products Inc., and is based entirely on National Climate Data Center (NCDC) weather stations. Only weather stations that contained monthly precipitation data from 1990 to 1998 for the months of March to October were selected. These months were used because they span the growing season, during which there can be a nearly direct trade-off between the amount of rain and the requirements for irrigation water application. The total precipitation for the months of March to October was then summed for each station to represent seasonal precipitation. The weather station data where then interpolated into 1 x 1 km precipitation grids across the High Plains aquifer region for each year, and the average precipitation value established.

Qualifications: The reported water use database maintained by the KDA-DWR is a very extensive and valuable data set. However, water use data are reported in a variety of fashions and at various levels of accuracy. For example, some water usage is based on a metered amount while other usage is calculated based on the number of hours pumped and the rate of water flow reported by the water user. As such, the values presented in this report represent only an estimate of the total amount of water used each year. Domestic wells and other small uses of water not subject to the appropriation process are not included in these totals, but this volume of water is unlikely to be significant relative to either the authorized or permitted use.

See also: Current Maximum Authorized Use, Percent of Authorized Quantity Used

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