Principal Investigator: Jack H. Reeves (The University of Georgia)
Principal Investigator: William P. McCormick (The University Of Georgia)
Sponsor: GWRI
Start Date: 1986-07-01; Completion Date: 1986-07-01;
Keywords: Low Flow Frequency, Design Flow, Time Series Analysis
Description:
In this report we analyze three problems related to a design low flow called the seven day, ten year minimum streamflow ,(7Q1O). The 7Q1O denotes the tenth percentile of the distribution of the streamflow, which gives for a one year period the lowest level of streamflow for which there was a seven consecutive day period with flows below that value on each day. The 7Q1O is commonly used as an annual design low streamflow for determining waste water discharge permit specifications.
The first problem we address is to determine monthly design low streamflow values. A method of assigning design low flow values which can vary over the year is of interest in order to allow greater use of the stream for diluting waste water discharges. We offer a simple method for calculating monthly design low flow values, which does not lead to any greater number of daily contraventions below the monthly design flows than that which already occurs for the one fixed annual 7Q1O method.
The second problem addressed concerns the estimation of 7QIO with a confidence interval. We offer a method based on a model for daily streamflows, and we compare our estimation procedure with two other often used procedures.
The third problem concerns the estimation of 7Q1O when the record of streamflow is only partial and short. We recommend a procedure which incorporates the use of rainfall data into our estimation procedure for 7Q1O.