INFLUENCE OF DIFFERENT TEMPORAL SAMPLING STRATEGIES ON ESTIMATING TOTAL PHOSPHORUS AND SUSPENDED SEDIMENT CONCENTRATION AND TRANSPORT IN SMALL STREAMS 1

Various temporal sampling strategies are used to monitor water quality in small streams. To determine how various strategies influence the estimated water quality, frequently collect- ed water quality data from eight small streams (14 to 110 km2) in Wisconsin were systematically subsampled to simulate typically used strategies. These subsets of data were then used to estimate mean, median, and maximum concentrations, and with continuous daily flows used to estimate annual loads (using the regression method) and volumetrically weighted mean concentrations. For each strategy, accuracy and precision in each summary statistic were evaluated by comparison with concentrations and loads of total phosphorus and suspended sediment estimated from all avail- able data. The most effective sampling strategy depends on the statistic of interest and study duration. For mean and median con- centrations, the most frequent fixed period sampling economically feasible is best. For maximum concentrations, any strategy with samples at or prior to peak flow is best. The best sampling strategy to estimate loads depends on the study duration. For one-year stud- ies, fixed period monthly sampling supplemented with storm chas- ing was best, even though loads were overestimated by 25 to 50 percent. For two to three-year load studies and estimating volumet- rically weighted mean concentrations, fixed period semimonthly sampling was best. (KEY TERMS: sampling design; strategies; frequency; water quali- ty; load; streams.)