WSP00905

• File Number: 8407.600
• Description: Platte River Basin - River Basin General Publications - Kansas General Publications
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 6/1/1965
• Author: Kansas Water Resourc
• Title: Kansas Streamflow Characteristics - Part 6A - Base Flow Data - Technical Report Number 6A
• Water Supply Pro - Doc Type: Report/Study

10

Because the need in Kansas is to determine the dependable supply of
streamflow, base flow in this report includes the ground-water flow com-
ponent and the delayed portion of interflow. Base flow, as defined herein,
means that flow of a stream that would exist if all the direct runoff were
extracted and precipitation continued to supply the usual accretions of flow
via the ground. Excluded by this definition is the early storm interflow or
temporary bank storage that infiltrates into the channel banks during a
flood only to seep back into the stream shortly thereafter.

Uses of base-flow data.--The most important use of base-flow data is
in forecasting total streamflow. Such forecasts consist of either an esti-
mate of a future discharge for operational problems or the probability of
occurrence of some given discharge for design problems. Base-flow data
are used in an analysis instead of total-flow data if upstream use of direct
runoff is anticipated. Examples of the two types of problems are given in
the following sections.

Typical operational problems include those of cities that obtain their
water supplies from streams. Here a knowledge of the expected flow would
provide the basis for determining whether or not supplemental supplies
might be needed. In areas where industrial and municipal wastes are dis-
charged into streams, low stream discharge could cause a serious pollu-
tion problem. Here again, a knowledge of future flow would aid in deciding
if temporary storage of the wastes is desirable. In some areas much of
the irrigation water comes directly from streams with little or no storage.
Estimates of expected flows could be used by administrators of water laws
to predict when flows would not be sufficient to satisfy the demands of ap-
propriators. Long-range forecasts of expected flows could be utilized in
the planning of acreage to be irrigated. In each case, estimated base flow
would be used in the analysis if direct runoff was extracted upstream, with
the base flow being modified, if necessary, by the direct runoff expected.

Estimates of the probability of occurrence of some specific discharge
or the probability of failure to maintain some given discharge are used in
the design of most water projects. The estimating of the probability of
occurrence of a specific discharge is closely tied to and usually done in
conjunction with the forecasting of future discharge. The probability of
failure of a stream to maintain sufficient flow for the water-supply needs
of a city must be considered when selecting one source of water over an-
other. This same probability would be used in the design of the supplysys-
tem and considered in locating an industrial site. The probability of fail-
ure to maintain sufficient flow would be a factor in the design of treatment
plants for the disposal of sewage and industrial wastes. Knowledge of the
probabilities of various low flows would aid in determining if a stream is