Simple Method for Streamflow Disaggregation

Abstract

Streamflow disaggregation from monthly to daily was performed using a relatively simple, flexible, and adaptive method. Only streamflow acts as a decision variable in this disaggregation process. To disaggregate monthly to daily flow at the target station (TS), monthly counterparts at the source station (SS) were selected on the basis of minimum error criteria, which are calculated with respect to streamflow volume within a three-month time window. Daily streamflow indexes at SS were then calculated to disaggregate monthly to daily streamflow at TS during the disaggregation process. The effectiveness of the proposed method has been demonstrated through its application at both regulated and unregulated waterways located in the northwest states, including Idaho and Wyoming. For both regulated and unregulated monthly streamflow, the proposed method well represents daily streamflow realizations similar to historical flows and preserves both mass balance and a series of statistical characteristics. However, the results also indicate that the quality of disaggregated daily streamflow varies for individual applications depending on the selection of stations, their geographic information, and data availability. The disaggregation model used in this research is transparent, user friendly, less intensive, and less time-consuming so that it can be used at any watershed without difficulty or much effort. Consequently, because development and availability of daily streamflow is important for water resources planning and management, including reservoir operation, water quality study, and environmental/ecological modeling, this research will help bridge the gap among interdisciplinary water research activities, especially for studies of the impacts of hydrologic events possibly driven by extreme weather variability and climate change.