WSP02699 - Laserfiche WebLink

Home Browse Search

tion of principal streams is necessitated by the extremely low runoff per unit area in the western part, which is generally less than I inch per year and less than one-tenth of the unit runoff in the extreme eastern part of the State. Definition of flow characteristics of minor streams must be accomplished by some process of generalization, because of the large number of such streams in the State. For natural streams this can be done by gaging at sample locations and relating the observed flow characteristics to basin characteristics to provide definition for ungaged streams. The effect of regulation and diversion on minor streams must also be generalized. Techniques of generalization normally cannot be used for principal streams because of higher accuracy requirements. The proposed approach here is to operate a network of gaging stations at selected locations on princi- pal stre'ams and, by interpolation or systems studies, to determine the flow characteristics at locations between stations. The procedure for defining the network of principal stream stations was as follows: (I) the first station on each stream was selected at the most upstream location where the drainage area was about 500 (1,000) sq mi and (2) were selected In a down- stream direction at points where the drainage area had approximately doubled (or more than doubled due to large tributaries entering the main stream). Long-Term Streamflow Data A long continuing series of consistent observations of streamflow is needed for two purposes: (I) analysis of the statistical structure of the hydrologic time series, and (2) as a reference or comparative base for noting changes in the regime at streams whose drainage basins or flows are developed for use. Statistical statements on flow characteristics are based on the assump- tion that the data series is stationary in a statistical sense, and that the observed record is a representative sample of the population of flows. Long-term homogeneous streamflow data would provide a basis for checking these assumptions and for adjusting flow characteristics from short records to more nearly represent the characteristics of the flow population. For these purposes the stations should be located on streams draining basins that have undergone no significant manmade changes, and that are expected to remain in a comparable condition in the future. The stations should be well distributed areally and should be located in basins having different physical characteristics. Environmental Data Stream discharge and water use are intimately related to the environ- ment in which the water occurs. Environmental data Include a wide variety of water-related information other than stream discharge. These data are 12