Estimating storm discharge and water quality data uncertainty: A software tool for monitoring and modeling applications

Uncertainty estimates corresponding to measured hydrologic and water quality data can contribute to improved monitoring design, decision-making, model application, and regulatory formulation. With these benefits in mind, the Data Uncertainty Estimation Tool for Hydrology and Water Quality (DUET-H/ WQ) was developed from an existing uncertainty estimation framework for small watershed discharge, sediment, and N and P data. Both the software and its framework-basis utilize the root mean square error propagation methodology to provide uncertainty estimates instead of more rigorous approaches requiring detailed statistical information, which is rarely available. DUET-H/WQ lists published uncertainty information for data collection procedures to assist the user in assigning appropriate data-specific uncertainty estimates and then calculates the uncertainty for individual discharge, concentration, and load values. Results of DUET-H/WQ application in several studies indicated that substantial uncertainty can be contributed by each procedural category (discharge measurement, sample collection, sample preservation/storage, laboratory analysis, and data processing and management). For storm loads, the uncertainty was typically least for discharge ( 7–23%), greater for sediment ( 16–27%) and dissolved N and P ( 14–31%) loads, and greater yet for total N and P ( 18–36%). When these uncertainty estimates for individual values were aggregated within study periods (i.e. total discharge, average concentration, and total load), uncertainties followed the same pattern (Q < TSS < dissolved N and P < total N and P). This rigorous demonstration of uncertainty in discharge and water quality data illustrates the importance of uncertainty analysis and the need for appropriate tools. It is our hope that DUET-H/WQ contributes to making uncertainty estimation a routine data collection and reporting procedure and thus enhances environmental monitoring, modeling, and decision-making. Hydrologic and water quality data are too important for scientists to continue to ignore the inherent uncertainty. Published by Elsevier Ltd. Software/data availability also available from Daren Harmel, 808 E. Blackland Rd., Temple, TX A Beta version of DUET-H/WQ was used in all analyses presented. Bill Komar, programmer with AgriLife Research part of the Texas A&M University System, completed the development in December 2007. This and future revisions are available at no cost online in an open source format at ftp://ftp.brc.tamus.edu/pub/ outgoing/bkomar/programs/. The software with the interface is . Harmel), douglas.r.smith@ .W. King), [email protected]. 76502, USA. Tel.: þ1 254 770 6521, [email protected]. DUET-H/WQ is written in Visual Basic and is distributed as an installable Windows file that requires the Microsoft.NET 2.0 Framework with Service Pack 1.