Unbiased Estimates and Confidence Intervals of Riverine Loads for Low‐Frequency Water Quality Monitoring Strategies

Abstract

Eutrophication in semiclosed water bodies, such as lakes and estuaries, due to excessive nutrient loads has severely damaged the ecosystem via water pollution. The establishment of pollution prevention measures in ecosystems requires accurate estimates of the total mass of pollutants flowing into a water body during a certain period. Because rivers are the main transport paths of pollutants to a receiving water body, accurate load estimation methods for riverine constituent loads have been studied over the past four decades. These studies assumed that river discharge was observed at a high frequency, such as daily, hourly, or subhourly, but water quality (WQ) is generally observed at a low frequency, such as weekly or monthly, due to the high cost and labor requirements for sampling and analysis. This mismatch among observation frequencies can result in highly uncertain load estimates.The low-frequency sampling methods used for load estimation include autosampling, stratified sampling (Thomas