Hydrologics Presents

Risk Management for Municipal Water Supply

Understanding the Role of Risk Management and the Limitations of Safe Yield in the Planning and Operations of Municipal Water Systems

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Water Supply System Evaluation



HydroLogics specializes in assisting clients to develop innovative, yet practical solutions to complex environmental planning, management and design problems. Complete resource analysis, including consideration of multiple conflicting objectives and integrated system management, can significantly improve overall benefits.


Planning for an adequate water supply continues to be a challenge as water demands and supply reliability continue to change. Sound planning needs to consider both the "physics" of the system (that which nature controls — size, amount of rainfall, etc.) and the operation of the system (that which humans control — when and how much water to release from a reservoir, when and how much water to divert to irrigators, and so on). The old adage, "An ounce of prevention is worth a pound of cure," certainly applies to the management of water supply systems. Sound planning now can prevent years of havoc.

High quality planning studies can answer many of the water supply and quality questions which are important to water suppliers. We believe that the best way to answer these questions is through modeling. OASIS, which is the centerpiece of our planning work, allows us to model virtually any water supply system, quickly, accurately and inexpensively.

Long-term Planning
Our primary method of long-term planning is to run OASIS for some period of record, the longer the better. In essence, a fixed level of demand (i.e., current or estimated for some time in the future, such as 2020) is imposed on 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. One of the important, and possibly unique, aspects of our long-term planning studies is to use forecasts of streamflow to help guide the system.

Short-term Planning
Short-term planning, often called real-time planning, is often facilitated by using a technique call "position analysis" which was developed by HydroLogics in cooperation with the USGS. In using position analysis we frequently generate a number of streamflow forecast traces for the system to be studied. The model is then run for a comparatively short duration, typically one year, with each of the traces. From this we can determine, given the state of the system today, the likelihood of the system being at a particular state at some prescribed time in the future.

Alternatives Evaluation
When studying methods to enhance water supply, there are typically a number of alternatives that need to be evaluated. While every water resources system is unique and requires an individualized approach, HydroLogics has developed a general approach for developing an understanding of the client's problem and evaluating both facility and operational alternatives to assist in the development of innovative solutions.

Operations Rules Development
A very important aspect of any system operation is to experiment with new operating policies to meet new objectives or to incorporate new operation constraints. Modeling can expose inefficiencies in operating policies and help identify more efficient operating rules. Our experience shows that more efficient methods of operating the system, often through cooperation with neighboring agencies, can dramatically increase the amount of usable water in a system. In some cases improvements in operating policies have forestalled huge capital expenditures.


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