Forecast-Based Water Supply Planning and Management to Improve Drought Reliability
- W. Josh Weiss, Ph.D., P.E., Ben Wright, P.E. - Hazen and Sawyer
Traditionally, municipal water supply planning has focused on assuring reliable sources of water to meet all but the most extreme demands under the drought of record. Systems have been designed to deliver peak daily demands by evaluating distribution limitations and to meet long-term demands by developing sufficient storage or other reliable sources. As demand increased or new, record hydrologic conditions were experienced, new facilities were constructed to both meet the peak demands and seasonal (or over seasonal) requirements.
Today, changes in water supply related to climate change, limitations on acceptable new reservoir sites, depletion and restriction of groundwater sources, rising development costs, and growing public concern for environmental impacts has refocused the emphasis from new sources to better management of existing supplies. These challenges have focused attention on two issues, the value of using emerging weather forecasts to inform decision making and the use of demand and operational modifications to extend the resources that we have.
Identifying the onset of a drought can be subtle, requiring detection of depletions of supplies and/or increases in demand. This can be made more difficult by the inability to make reliable, long-term weather forecasts and the lack of practice in managing drought. A delay in instituting a drought response can limit the range of possible actions if drought does occur. In contrast, early preventative actions may result in needless expenses or a loss of revenue. Water managers must be prepared to take appropriate action but not willing to impose unnecessary responses when they are not warranted.
This paper will explore the availability and utility of drought index and forecast products for different regions of the US and will suggest a framework by which water supply managers and operators can use forecasts and early-warning drought indices to better prepare for extended drought conditions.
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