A Tale of Two Basins
Comparison of California’s Bay-Delta and the Murray Darling Basin
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The Murray-Darling Basin is the breadbasket for Australia much the same way as the Sacramento-San Joaquin Basin is a primary breadbasket for the United States. And just like in California, complex issues like water allocation, climate change, water quality, salinity, and environmental degradation are at the forefront of water resource planning in the Murray-Darling Basin. A comparison of the issues facing both basins was the topic of a special lecture symposium held recently in Brisbane, Australia.
CALFED lead scientist Cliff Dahm participated in this symposium hosted by the Australian Rivers Institute in Brisbane, Australia. Dahm discussed the role of science in integrated river basin management in the Sacramento-San Joaquin Basin, and Rob Freeman, the Chief Executive of the Murray-Darling Basin Authority, discussed the role of science in the Murray-Darling Basin Plan and the planning process to bring integrated and sustainable management of water resources to the Murray-Darling Basin by 2011.
Comparisons Between the Murray-Darling Basin and the Sacramento-San Joaquin Basin
The Murray-Darling Basin covers more than one million square kilometers (km) or about 386,000 square miles in size, making the basin more than two and one-half times the size of the State of California. For comparison, the Sacramento-San Joaquin Basin is about 155,000 square km (about 60,000 square miles).
The Murray River and Darling River system is 2,097 miles long (3,375 km) compared to a length of 748 miles (1,204 km) for the Sacramento River and San Joaquin River system.
Only about 4 percent of the precipitation that falls within the Murray-Darling Basin produces runoff, and only about 2 percent or five million acres of the basin is irrigated. Diversions of water within the basin total a little more than half of total runoff. By comparison, approximately 28 percent of the precipitation that falls in the Sacramento-San Joaquin River Delta watershed produces runoff. Water diversions also total a little more than half of total basin runoff during an average year in the Sacramento-San Joaquin Basin, irrigating about three million acres and providing drinking water for 25 million Californians.
The city of Adelaide is located at the end of the Murray-Darling Basin where the Murray River meets the ocean. As a result, the river that is an important source of water to the city is threatened by increasing salinity. Salinity increases in the Murray-Darling are due to removal of native vegetation and a rising water table that brings salts to the surface from below. Bay-Delta drinking water is also threatened by potential for salinity increases in the near term from ocean saltwater intrusion due to Delta levee failure and longer term from sea level rise.
Agriculture is the dominant economic engine in both basins with one-third of Australia’s food supply produced in the Murray-Darling and 40 percent of the fruits and vegetables in the U.S. coming from California Central Valley agricultural land.
Scientists and decision makers in both countries can benefit from awareness of common problems and approaches being implemented to meet these challenges.
Major planning efforts are occurring in both basins. The Basin Plan for the Murray-Darling Basin, the Delta Vision Strategic Plan, and the Bay-Delta Conservation Plan have many common themes. For example, the Basin Plan for the Murray-Darling Basin must, by law, address:
- Limits on the amount of both surface water and groundwater that can be taken from the basin.
- Risks to basin water resources such as climate change.
- Coordination and compliance between states.
- An environmental water allocation plan to optimize environmental outcomes.
- Water quality and salinity management.
- Rules for water trading.
Delta Vision, formed in 2007 under an executive order by Governor Arnold Schwarzenegger, was charged to “develop a durable vision for sustainable management of the Delta.” Delta Vision was intended to identify a strategy for managing the Sacramento-San Joaquin Delta as a sustainable ecosystem that would continue to support environmental and economic functions that are critical to the people of California.
In comparison, some of Delta Vision's recommendations include:
- California’s water supply is limited and must be managed with significantly higher efficiency to be adequate for its future population, growing economy, and vital environment.
- The goals of conservation, efficiency, and sustainable use must drive California water policies.
- A revitalized Delta ecosystem will require reduced diversions — or changes in patterns and timing of those diversions upstream, within the Delta, and exported from the Delta — at critical times.
- Major investments in the California Delta and the statewide water management system must integrate and be consistent with specific policies in this vision. In particular, these strategic investments must strengthen selected levees, improve floodplain management, and improve water circulation and quality.
- Institutions and policies for the Delta should be designed for resiliency and
adaptation.
The goal of the Bay Delta Conservation Plan (BDCP) is to provide for both species/habitat protection and improved reliability of water supplies. The plan will identify a set of water flow and habitat restoration actions to contribute to the recovery of endangered and sensitive species and their habitats in California's Sacramento-San Joaquin Delta. The BDCP is being developed in compliance with the Federal Endangered Species Act (ESA) and the California Natural Communities Conservation Planning Act (NCCPA). When completed, the BDCP would provide the basis for the issuance of endangered species permits for the operation of the state and federal water projects.
The BDCP is:
- Identifying conservation strategies to improve the overall ecological health of the Delta.
- Identifying ecologically friendly ways to move fresh water through and/or around the Delta.
- Addressing toxic pollutants, invasive species, and impairments to water quality.
- Establishing a framework and funding to implement the Plan over time.
Adaptive management frameworks that include active evaluation of research results, targeted research on topics of concern, and improved understanding through synthesis and analysis also are recommended as critical components to the developing basin plans.
Another clear area of similarity between the basins is the growing concern about the link between water resources and climate change. Global climate change has created a new normal in the Murray-Darling Basin. This has necessitated new water law and a new governance system to allocate water within this part of Australia. A comprehensive basin plan is mandated for development to allocate this increasingly scarce resource. Similarities with water issues in California are striking. Climate change, water allocation, and governance also are at the heart of water policy decision making in the Bay-Delta. We have much to learn from each other. Agriculture in these breadbaskets of the world will be challenged to adapt to a changing climate.
