City of Los Angeles - the Green Blue City One Water Program, Part 1 of 5: Abstract, Introduction, Water Supply - Imported Water

摘要

The City of Los Angeles, with a population of over 4 million people, covering an area of over 400 square miles, is in a semi-arid region with a Mediterranean climate where local rainfall occurs over the course of a handful of storm events between October and May of each year. As such, the infrastructure has been developed to import water from Northern California and the Colorado River to provide water supply, and to route storm flows from the developed lands in the City to the Pacific Ocean rapidly and efficiently. This infrastructure has resulted in the development of one of the world's megacities as defined by the University of Southern California's Center on megacities. While the City enjoys protection from flood risks and a dependable water supply of imported water, the receiving waters within the City suffer from impairments and numerous Total Maximum Daily Load (TMDL) regulations are being promulgated compelling the City to improve the quality of its stormwater runoff to lower the pollutant discharges from its urban streetscapes. Additionally, the imported water supplies that the City enjoys are expected to not be expandable and, with impending climate change modifying Sierra snowpack storage and state-wide meteorology, may decrease with time. To meet both challenges, the City has put in place water management programs to reduce reliance on imported water supplies and to prevent the discharge of pollutants onto and from its streets and storm drain systems. The program is moving the City toward water sustainability and is being termed as the Green-Blue City of Los Angeles Water Management Program. The program consists of several elements: 1. A low impact development ordinance requiring most new and re-development to retain, infiltrate, evapotranspirate, and/or use on site the volume of water from the 85th percentile storm. This represents the most of the storm events that occur and the largest storm expected to occur in most years. 2. An enhanced watershed management planning program where regional and distributed projects are being planned to capture and infiltrate, evapotranspirate, and/or use the volume of water from the 85th percentile storm from areas that do not have such systems on private parcels. 3. A $500 million dollar voter approved bond funded program to build capital projects throughout the City to capture and use or treat urban runoff and stormwater. This bond fund is referred to as proposition O and was passed in 2004. Since passage of the measure, the funds have been allocated to projects and most of those projects have bee built. Most of the projects have multiple benefits derived from the use of green StormWater infrastructure. The projects include: 3.1 South Los Angeles Wetland Park Project 3.2 Cesar Chavez Recreational Complex 3.3 Hansen Dam Recreational Area Parking Lot And Wetlands Restoration 3.4 Echo Park Lake Rehabilitation Project 3.5 El Sereno Parking Grove 3.6 Cabrito Paseo Walkway & Bike Path 3.7 Los Angeles Zoo Parking Lot 3.8 Rory M. Shaw Memorial Wetlands Park (formally Strathern Wetlands) 3.9 Wilmington Drain Multi-Use Project 3.10 Machado Lake Ecosystem Rehabilitation Project 3.11 Rosecrans Recreation Center Stormwater Enhancements 4. Development of standard plans and specifications for green streets features for new and re-development and for street right of way improvements. 5. Development of a recycled water master plan with goals of more than doubling the amount of wastewater recycling with drinking water aquifer recharge as a significant element. 6. Development of a stormwater capture master plan with goals of capturing local stormwater for recharging drinking water aquifers or direct use where feasible throughout the City.