Integrated assessment of water conservation practices for sustainable management strategies

Miami-Dade County implemented a series of water conservation programs, which included rebate/exchange incentives to encourage the use of high efficiency aerators (AR), showerheads (SH), toilets (HET) and clothes washers (HEW), to respond to the environmental sustainability issue in urban areas. This study first used panel data analysis of water consumption to evaluate the performance and actual water savings of individual programs. Integrated water demand model has also been developed for incorporating property’s physical characteristics into the water consumption profiles. Life cycle assessment (with emphasis on end-use stage in water system) of water intense appliances was conducted to determine the environmental impacts brought by each practice. Approximately 6 to 10 % of water has been saved in the first and second year of implementation of high efficiency appliances, and with continuing savings in the third and fourth years. Water savings (gallons per household per day) for water efficiency appliances were observed at 28 (11.1%) for SH, 34.7 (13.3%) for HET, and 39.7 (14.5%) for HEW. Furthermore, the estimated contributions of high efficiency appliances for reducing water demand in the integrated water demand model were between 5 and 19% (highest in the AR program). Results indicated that adoption of more than one type of water efficiency appliance could significantly reduce residential water demand. For the sustainable water management strategies, the appropriate water conservation rate was projected to be 1 to 2 million gallons per day (MGD) through 2030. With 2 MGD of water savings, the estimated per capita water use (GPCD) could be reduced from approximately 140 to 122 GPCD. Additional efforts are needed to reduce the water demand to US EPA’s “Water Sense” conservation levels of 70 GPCD by 2030. Life cycle assessment results showed that environmental impacts (water and energy demands and greenhouse gas emissions) from end-use and demand phases are most significant within the water system, particularly due to water heating (73% for clothes washer and 93% for showerhead). Estimations of optimal lifespan for appliances (8 to 21 years) implied that earlier replacement with efficiency models is encouraged in order to minimize the environmental impacts brought by current practice.

Flow and water budgets in the C-111 and L-31W canals near the Everglades National Park, Dade County, Florida

Acoustic velocity meter (AVM) sites, located both distant and adjacent to canal water control structures, were constructed and calibrated in L-31W borrow canal and Canal 111 (C-111) to measure canal water velocity. Data were used to compute monthly discharge volumes and overall water budgets for several canal reaches from August 1994 to May 1996. The water budgets indicated extensive aquifer inflows in L-31W associated, in part, with S-332 pump station return flows. Canal and groundwater piezometer data showed 5 distinct hydrologic scenarios (distinguished by the direction and magnitude of hydraulic gradients) in the important Frog Pond area on the eastern boundary of the Everglades National Park. Most of the water lost from C-111 was via surface water losses near the outlet of the system, close to Florida Bay. The distribution of flows during the study suggest an alteration of the present South Dade Conveyance System modification plan to improve water deliveries to Taylor Slough and the Eastern Panhandle of the Everglades National Park. ^