The convolution integral is used to compute continuous variations in channel loss and base flow that result from a reservoir release on the North Canadian River in central Oklahoma. The open channel flow hydrograph is routed by using the unit response method and then modified for interaction with the aquifer. Stream losses and gains are evaluated from the arbitrary fluctuations in stream stage by using average values of aquifer parameters. In spite of gross simplification pertaining to the nature of the groundwater system, good agreement with the actual flow hydrograph is obtained.

In fitting a theoretical frequency distribution to a set of data, a problem arises if the series contains a number of zero values, as may occur in annual flood peak data for small, arid-region streams. The problem is twofold: first, commonly used distributions do not fit such a set of data; second, if a logarithmic transformation of the data is being used, logarithms of zero flows are not usable in a computation. To overcome the difficulties, a theorem of conditional probability is used. The probability of occurrence of a nonzero peak is combined with the conditional probability of exceeding a given flood magnitude, given that a nonzero peak has occurred. The method has been found useful also for fitting flood series in which information of peak annual floods below a specific stage is lacking.

Thirty‐one streamflow water quality stations in Texas, with long‐term historical records ranging from 7 to 28 years, were selected for statistical analyses of the annual mean concentrations of the major chemical constituents. A statewide multiple regression analysis using frequency characteristics of annual mean water quality constituents as dependent variables and selected basin characteristics as independent variables was investigated as a means of regionalizing information on annual water quality characteristics. For the two different regression models investigated, a single independent variable, generally stream discharge or average basin rainfall, explained a significant part of the variance of the dependent water quality variables. Areal analysis of residuals of the statewide regression models indicated two distinct regional patterns. Correlation coefficients for the concentration‐rainfall regional models ranged from 0.80 to 0.97 and the standard errors of estimate were between 26 and 99% of the means of the dependent variables. An analysis of various concentration‐conductance relationships for the statewide data also gave favorable results, and provided an alternate method for obtaining estimates of streamflow chemical quality characteristics.

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Studies to determine frequency characteristics of regulated streams at points within a stream system require the use of flow routing models. This study compares several different flow routing methods using data from six river reaches. Results indicate that approximate flow routing methods yield good flow estimates when compared with observed flows. The unit response method, recently introduced, performed as well as other approximate methods for all reaches studied and gave better results for reaches subject to power releases.