Using an End Use Model to Quantify Demand Hardening fromLong-Term Conservation Programs

摘要

This paper describes experiences and new learning from working with end use models torndetermine the loss in effectiveness of drought water reduction measures caused by thernimplementation of long-term conservation programs.rnWater managers have long been concerned that funding long-term conservation programs, andrnusing the saved water to allow for new growth in connections, will make it more difficult tornreduce consumption during water shortages (droughts). It is generally thought that high levels ofrndemand cut-backs requested and achieved in the 1970’s-1990 could not be repeated becauserncustomers have become more water efficient. Future planning for new water supply generallyrnassumes that a lower level of drought cut-backs must be planned for, i.e., the excellent responsernby customers in the past can not be counted on to be replicated in the future.rnThe goal of the paper is to show how modeling water use and customer behavior at the end usernlevel enables a realistic assessment of just how much cut-backs in demand can be expected andrnhow those cut-backs are reduced due to the efficiency improvements obtained through long-termrndemand reduction programs.rnThe paper will provide the following types of information, drawn from completed projects:rn1. How to model a drought cut-back ordinance as a short-term conservation measure.rn2. Which end uses can still be reduced in a droughtrn3. How short-term and long-term end use reductions interactrn4. Typical magnitudes of demand hardening as a function of the amount of long-termrnconservation implemented or planned.rn5. Realistic expectations for customer cut-backs in droughts in say 2025, afterrnaggressive long-term conservation programs have been implemented.rnThe Least Cost Planning Demand Management Decision Support System, or DSS model, an endrnuse cost-benefit tool, has been used for 150 projects over the past nine years. Only recently hasrnit been used to model demand hardening. Findings to-date are showing that drought ordinancesrnthat call for say a 25 percent short-term demand reduction might only achieve 21-22 percent cutbacksrnif the plumbing and appliance codes and long-term programs together will save about 15rnpercent. That is the demand hardening is only a few percent in this situation. Howeverrnexpectations of achieving temporary 35 percent cut-backs, as in the past, are not realistic. Thernuse of an end us model will reduce the amount of guess work currently required in drought andrnsupply planning, and reduce one impediment to funding long-term water conservation programs.