Apr
23
Key Water Issues Now Facing our Nation
April 23, 2008 | Posted by admin
Robert M. Hirsch, Timothy L. Miller, Pixie Hamilton, and Robert Gilliom
Series: Water Resources in the Next Decade
Challenges to sustaining sufficient and high-quality water for human consumption, industry, farms, energy production, and ecosystem services continue to intensify in many parts of the Nation. We face four key water issues that call for support from the science and engineering communities.
- Streamflow to Support Aquatic Ecosystems. The historic question in water-supply development was “How much water can we take from the river on a reliable basis?” The contemporary question is “How much water do we need to leave in the river to support and sustain stream biota and habitat?” Far more than a question of minimum in-stream flow requirements, this challenge involves the entire hydrograph, interactions of flow conditions with channel form and water quality, and the consequences of these changes on ecosystems.
- Sustainable Ground-Water and Surface-Water Supplies. Historically, ground-water resources were tapped with little consideration to aquifer-storage depletion or streamflow effects. Now, ground-water storage is diminishing in many aquifers, resulting in higher pumping- lift costs, land subsidence, saltwater intrusion, and reduced streamflow. The contemporary question is “How do we manage ground water and surface water as a single sustainable resource?” To answer this question, we must expand systematic collection of data for tracking water resources, develop reliable hydrologic models for analysis of the interconnected ground-water and surfacewater systems, and evolve legal and economic institutions that consider the whole interconnected resource.
- Sustainable Water Quality. Since implementation of the Clean Water Act in 1972 point sources have been largely controlled for regulated contaminants, and waterquality concerns have increasingly focused on difficultto- control nonpoint sources of pollution, such as agricultural and urban runoff, and atmospheric deposition. Possible causes of impairment can include: changes in flow, increases in water temperature and salinity, presence of natural or anthropogenic chemical contaminants (including those at concentrations that are not lethal but may have adverse effects on humans or aquatic life), invasive species, riparian disturbance, and construction of physical barriers. The analysis of changes in water quality is complicated by the fact that variations due to normal fluctuations between wet and dry periods can overshadow the human influences. The contemporary question is “Can we identify which causes of impairment are dominant so we can successfully manage our water resources?”
- Effects of Climate Change. We have managed and developed water resources on the premise that water resources behave in a stationary and relatively predictable manner foretold by historical data. However, we now see that both short-term and long-term hydrologic variability is the norm, ranging from natural short-term climate swings related to El Niño to long-term changes associated with increased greenhouse gas concentrations. These influences can change the magnitude and timing of streamflow, which in turn changes the reliable supply for human and ecosystem uses. The contemporary question is “How do we manage water resources knowing that hydrologic processes are not stationary and our current ability to make reliable predictions is limited?’
Two needs stand out as we attempt to address all of these challenges. First, credible long-term data and assessments are needed to understand our water resources and how they are changing through time. In addition to water quantity and quality data, we also need ancillary data on landscape features and human activities related to chemical, land, and water use.
Second, we need to accelerate the development of reliable predictive models to understand water resources in places and times that we cannot feasibly monitor, and to determine how resources will change as a result of our water management decisions and actions. These models must have a strong basis in theory but be guided by long-term observational data. Science and technology have been crucial to the development of our water-resources infrastructure and improvements in water quality to date. Science and technology are central to resolving the water issues that we face today.
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In many areas these issues are not likely to get the attention needed to affect change. In the more arid regions of the country water rights issues dominate all of the discussions with little consideration of water quality. Overall, there are few immediate implications to not improving water quality or conserving water supplies.
On the second need, I’d say we have an over-reliance on predictive modeling at the expense of scenario-based forecasts. In such a capricious environment as ours, uncertainty is all pervasive. Equifinality anyone? Sure, we should reduce this uncertainty, but I’d say we should also reduce our demand for certainty - improve resilience.
I certainly agree with this summary of key water issues facing the U.S. The impacts of regional climate change on streamflow regimes of individual river basins is the focus of the company I have recently started: Hydrology Futures, LLC (http://hydrologyfutures.com). Because I believe there is a widespread need for simulations using state-of-the-art hydrologic models and the latest (IPCC, 2007) future climate scenarios, I have come from academia to the consulting world to effectively respond to this challenge.
i thing the sustainable water resource or development it is very important espaially in arid and semi arid zone (my country Sudan ). Any practies lead to increases the water ( surface water, groundwater and increase the use of rainfall water in agriclture it very important.