A Method for Developing Daily Flow Data from Monthly Model Output that can be Used for Risk Assessment
Project ID: 2582
Principal Investigator: Jennifer Johnson
Research Topic: Water Resource Data Analysis
Priority Area Assignments: 2011 (Climate Adaptation), 2012 (Climate Adaptation), 2013 (Climate Adaptation)
Funded Fiscal Years: 2011 and 2012
Is there an efficient and effective method for converting monthly flow data to shaped daily data that can be used for risk assessment? Often, flow data obtained from the Bureau of Reclamation (Reclamation) planning model output is in monthly increments (e.g., acre-feet per month). However, risk assessments, such as determining flood risk or meeting minimum flows for fish, require that data be in daily increments and that the minimum and maximum flow rates be estimated. Reclamation is in need of an accepted method in which to calculate daily flow data from monthly model outputs to be used for such studies.
Need and Benefit
Long-term planning and environmental studies are used to determine operating procedures under changing conditions (e.g., new environmental regulations, site structural changes, or global climate change). Numerical models allow Reclamation hydrologists to determine the impact of changes to the system and to evaluate possible reactions to changes in the system. Reclamation planning models are typically run using a large amount of historical data to statistically capture the range of recorded possible flow volumes and timing. These long- term planning models are run using a monthly time step to reduce overhead and also because daily input data is not typically available for the entire period of record.
Since a large number of planning studies are now asking for assessment of statistical probabilities of results such as exceeding flood stage, filling reservoirs, and going below minimum flow requirements for fish, it is necessary to develop daily data that capture the statistical likelihood of these events. Daily data are necessary because monthly data typically smooth over the peaks of a hydrograph, so the likelihood of these events would be greatly reduced and not accurate enough to satisfy study requirements.
By having a method that has been evaluated and accepted to develop daily data from monthly data, Reclamation hydrologists could be more efficient in meeting the requirements of planning and environmental studies.
Independent Peer Review
The following documents were reviewed by qualified Bureau of Reclamation employees. The findings were determined to be achieved using valid means.
Document ID 686: this document contains protected information and it cannot be freely downloaded from USBR.gov. Contact the Principal Investigator to request a copy of this document.