Evaluating the effectiveness of a water conservation program can be complicated. It requires both an analysis of the changes in water use associated with the program, but also of the many possible confounding effects that must be taken into consideration. For example, the water use in an intervention group may decrease, but the use in the general population decreased as well, and perhaps by more that that in the test group. In that case, the changes in the general use must be netted out of the gross changes observed in the test group. One must also take into accounts changes in weather or economic conditions during the study period. Aquacraft has experience dealing with complicated analyses in order to discover the real changes (either positive or negative) that can be attributed fairly to any conservation program. This type of analysis is essential for any thoughtfully run water conservation program.
In 2011 Aquacraft performed an evaluation of the installation of high efficiency toilets in multi-family households for the Southern California Edison Company. In this study we did a pre-post comparison of the amount of water used for toilet flushing before and after the installation. Since the same homes were used for the paired samples this eliminated the effects of thngs like residents or other factors because the only thing that changed was the installation of the new toilets. SCE HET EM&V Final
We have discussed the evaluation of the weather based irrigation controllers that we did for California. In this study we also used paired sample analyses to determine how the installation of WBICs changed the landscape water use in a large sample of homes in both Norhern and Southern California, and the factors that affected the amount and direction of the change.
Evaluation of California WBICs_Executive Summary
For the Castail Lake Evaluation pre-post analyses were done for both the test group and a control group. that consisted of the general populartion of single famil homes that did not receive a WBIC and which were within 500 feet of a WBIC installation. The results of the study showed that due to a number of factors, the economic slow down of 2008 being a prime factor, the water use in the test homes decreased, but that of the general population decreased by more. Castaic WBIC Report