Everyone knows it’s government’s job to protect the water in our lakes, rivers and aquifers from pollution. Governments set water quality standards and regulate pollution sources to ensure that those standards are met. But what about water quantity? The timing and amount of water flows are just as critical to healthy lakes, rivers and aquifers as the quality of that water. Increasingly, governments are realizing that it is equally their job to protect water resources from over-exploitation.
The Nature Conservancy is helping water management agencies throughout the world to adopt and implement scientifically rigorous water quantity standards or goals. While many jurisdictions already protect “minimum” flows in rivers, very few currently maintain environmental flows – the full range of inter- and intra-annual flow patterns upon which healthy freshwater ecosystems depend.
The Brisbane Declaration calls on governments of all nations to implement and enforce environmental flow standards. This entails:
1. Establishing a legal basis for environmental flow protection: Many states, provinces and countries have established a legal basis for protecting environmental flows, either as a reserve with its own special legal standing – as in South Africa – or as a beneficial use on par with other water uses, as in most of the western United States. Governments also need to statutorily close basins that already approach limits on flow alteration new water withdrawals, including both groundwater and surface water. To ensure that future developments in closed basins still have access to water, provisions need to be established for re-allocating water withdrawals between users and from offstream to instream use.
2. Quantifying limits on flow alteration: Legislating environmental flow protection is one thing; determining what those flows should be is quite another. Limits on flow alteration need to be credible, enforceable and linked to ecological health. Many countries whose laws protect environmental flows have yet to quantify flow requirements for most of their water bodies. To overcome the bewildering array and complexity of assessment methods, we recommend a hierarchical approach, or suite of assessment methods to match the sophistication of flow criteria to available capacity and the anticipated extent of flow alteration. At the base of the hierarchy, precautionary flow limits are rapidly determined for all water bodies, so that implementation can begin as soon as possible. ELOHA and the Sustainability Boundary Approach are specifically designed for this purpose. At the top of the hierarchy, detailed, sophisticated analyses of individual sites are carried out as needed to refine the initial estimates. Regardless of the approach, flow limits need to reflect stakeholder values.
3. Managing flows within the limits: Once limits of flow alteration are quantified, what are some creative water management strategies for implementing them?
An effective water-use permitting system ensures that withdrawals from a water body, plus all the withdrawals from upstream, do not conflict with stakeholder values – that is, environmental flows are always maintained. Because the amount of water available is a time-varying quantity subject to competing demands for water, a computerized decision support system is needed to link individual and cumulative withdrawals to flow targets. The Nature Conservancy guided the development of these “e-DSSs” (environmental-flow decision support systems):
- Michigan’s Water Withdrawal Assessment Tool (WWAT) links a groundwater model, surface water model, biological response model and water use database to determine the ecological risk of proposed new surface and groundwater withdrawals. It is available online, and its use is mandated for proposed new large withdrawals. The tool’s success in reducing the permitting burden on both government agencies and the public has earned it three national awards.
- Colorado’s Watershed Flow Evaluation Tool (WFET) also links flow-ecology relationships to streamflow. Stakeholders are using it to understand risk status for specific ecological attributes across entire watersheds at a reach or sub-basin scale.
- The Sacramento River Ecological Flows Tool (SacEFT) links flow management actions to focal species conditions to improve the ecological outcomes of water operations.
- The Massachusetts Sustainable-Yield Estimator (MA SYE) provides screening-level estimates of the sustainable yield of a basin, defined as the difference between the unregulated streamflow and a user-specified quantity of water that must remain in the stream to support such functions as recreational activities or aquatic habitat.
Dam design and operational requirements assure the release of water their reservoirs as needed to maintain downstream flow requirements.
Conjunctive management of ground water and surface water enables new water withdrawals while maintaining streamflows within prescribed limits. Innovative approaches supported by The Nature Conservancy: (More content coming soon.)
- Idaho’s Snake River Plain
- Oregon’s groundwater-dependent ecosystems
- Michigan’s water withdrawal management program
- Strategies for mitigating impacts of groundwater pumping on surface water resources due to:
Water conservation (with caution). Reducing water withdrawals does not always save water, and may in fact adversely impact freshwater ecosystems. Find out why. (Content coming soon.)
- Slate article on water conservation misconceptions.
- Kendy 2003 (Link coming soon.) – False promise of sustainable pumping rates
Monitoring and adaptive management (Content coming soon.)
