River Basin Management

Water Allocation

An important aspect of any water resources system are the policies that define how water is allocated between often-competing uses.  Through our time-tested framework for operating rules development, modeling can help identify more efficient operating rules. These rules, in turn, can dramatically increase the amount of usable water in a system, especially when cooperation with neighboring agencies is considered. In some cases, improvements in operating policies have forestalled huge capital expenditures.  In all cases, such improvements are deemed by the U.S. Environmental Protection Agency as a "no regrets" option for adaptation to climate change.    

Our primary method of long-term planning is to run the OASIS model for some representative current or future conditions, the longer the better.  Often, the record is defined by the historic hydrology, for which HydroLogics has considerable experience in developing.  Typically, we rely on U.S. Geological Survey (USGS) stream gaging stations (after adjusting for the historic impairments to those flows so we can have an unregulated record), and filling In the missing records using other highly-correlated gages. 

We then simulate the current or projected demands and operations over the hydrologic record to see how the system responds to that level of demand over time. From that we can determine how often certain events happen during the record. We can also look at alternative inflow data sets, including those that are adjusted for various climate change scenarios. 


One of the important and unique aspects of our planning studies is to use forecasts of streamflow to help guide the system.  We typically use use statistically-derived forecasts based on a USGS methodology, but if available for a sufficiently long period, we will also use forecasts derived from rainfall-runoff models like those used by the National Weather Service.

We then use OASIS to implement the rules, including forecast-based rules that rely on streamflow forecast traces that are run through OASIS in its “positional analysis”, or real-time operations mode, to generate probabilistic information about streamflows and reservoir storage on which managers can take action.

OASIS also provides a powerful tool for managing water markets and evaluating potential trades. Many economists and water purveyors believe that water markets are the solution to water allocation problems, but there is little agreement about what a water market should really look like. HydroLogics staff have been involved in the research and application of water marketing and in the investigation of potential trades.  

An example of a trade-off analysis between competing uses of water (water supply vs. environmental flows) during a drought.  The OASIS plot shows how reservoir storage will be impacted at different times in the future for a given minimum release scenario.  Additional OASIS runs can be made with alternative minimum releases to see how these drawdown projections are impacted, and releases can be adjusted accordingly depending on the risk tolerance of the water supplier.  

"i wish I had had OASIS in the last major drought to better quantify the risks."

Tom Frederick, former Director of the
Rivanna Water and Sewer Authority, Charlottesville, Virginia

© 2016 by HydroLogics