THE DEVELOPMENT OF RELATIONSHIPS BETWEEN CONSTITUENT CONCENTRATIONS AND GENERIC HYDROLOGICAL VARIABLES

Abstract

The collection and analysis of samples from storm events constitutes a large portion of the effort associated withwater quality research. Estimating concentrations or loads from these events is often difficult. The equipment necessary toanalyze the samples and the required laboratory resources are typically significant expenses incurred by the researcher. Onepotential method to reduce these costs is through the development of generic relationships between concentrations and easilymeasured variables such as dimensionless flow rate or time. The benefits recognized from such an effort include a reductionin the number of required samples, resulting in a reduction in cost. Using data collected from an Arkansas stream nearFayetteville, relationships between the generic variables (time and flow) and several constituents (nitrateN,orthophosphate, total phosphorus, ammoniaN, total Kjeldahl nitrogen, chemical oxygen demand, total suspended solids,fecal coliforms, and fecal streptococci) were examined. Results of the analyses indicated that a form of the gamma functioncould be used to estimate the flowweighted mean concentrations and loads of the constituents at a significant cost savingsto the user, assuming that singlepeak hydrograph data were readily available. By using a single sample collected at the peakof the storm along with information pertaining to the time of sample collection, time of the peak of the storm hydrograph, andthe constituent concentration of the sample, the flowweighted mean concentration or load could be determined. Results ofthe analysis indicate that the method performed reasonably well. Since the analysis of only one sample is required to determinethe flowweighted mean concentration or load, instead of several samples, this method is quite appealing to users on a limitedbudget.