the crucial link between water quantity and quality - world water
TRANSCRIPT
World Water Week 2010
Workshop 2: Shortcutting Historical Pollution Trends
September 9, 2010
Daniel Stellar
Assistant Director, Columbia Water Center
The Crucial Link between Water Quantity and Quality: The Scope of the Problem and
Implications for Solutions
Motivation Explicitly draw out the link between water quality and
quantity
Demonstrate how interventions which affect water quantity can also improve quality, thereby “shortcutting historical pollution trends”
Context Many ways exist to provide safe, high quality water Limiting source pollution Providing treatment
These methods are resource constrained by, money, energy and /or regulatory environments
In some cases there is also a conservation- oriented, quantity-based solution
Quality problems are not always triggered by external pollutants – they can be caused by depletion of quantity
Examples of water quality-quantity tradeoffs Groundwater Excessive pumping of groundwater leading to decreased quality,
through saltwater intrusion and increasing concentration of TDS’s Israel / Palestine - Gaza Coastal Aquifer Cyprus
Surface water Overuse of river water reduces flows leading to increased
pollution concentrations Iraq –Tigris River US / Mexico – Rio Grande River
Context
Water scarcity exacerbates pollution and degradation
Reducing depletion of water resources improves water quality and access
Columbia Water Center is working on all 3 of these areas directly and indirectly. By addressing the root problem of water scarcity we are driving solutions to pollution and access.
3 Nested Water Crises
Case study: Gujarat Semi-arid region Relatively hot and dry, with
low average annual rainfall
Significant ongoing groundwater depletion
Energy use heavily subsided by state. Groundwater depletion so severe that
value of subsidy exceeds farmers income from crop
Example: Gujarat Water levels falling with regard to
mean sea level
In our sample, 82 % of wells reported the appearance of salt in their water over the last 5-15 years. Other changes in water quality include fluoride (30 %) and dust (30 %).
Other studies demonstrate increasing levels of salt and a high level of fluoride in water sources across Gujarat.
Example: Gujarat Project description:
Target agricultural use and water-energy nexus
3 part campaign, including education, analysis of technology options and incentive-based system Reforming energy subsidy can
encourage conservation by farmers
Revenue neutral approach emphasizing incentives for conservation instead of pricing or taxing
Example: Gujarat Possible results: Water savings of up to 10-30%
Reduction in energy use leads to stabilization of groundwater tables at a higher level, reducing risk of catastrophic saltwater intrusion
Gradual increase in groundwater tables, eventually leading to improved quality of groundwater
In this case, quality problem can be avoided by addressing quantity problem.
Quality – quantity interactions
“Pure” Water Quality Problems
•Charles River, MA, USA
Water Quality Problems with Strong Quantity Component•Gujarat, India•Rio Grande
As scarcity increases, so does importance of quantity-quality tradeoffs, and there is a greater role for conservation oriented reforms
Ganges River Yangtze River
Solutions When might a conservation-oriented, quantity based
approach work? Subset of Water Quality Problems with Strong Quantity
Component
Water scarce environment Significant ongoing use of water Agriculture is driving water use Efficiency gains are possible
“Pure” Water Quality Problems
Water Quality Problems with Strong Quantity Component
Conclusions In some cases, water quality problems are caused or
exacerbated by insufficient water quantity In a subset of these cases, conservation-oriented approaches
aimed at restoring quantity may be the most appropriate solution
Water scarcity is likely to exacerbate importance of quality-quantity tradeoffs
Recognizing these issues, and addressing them directly, can allow for shortcutting of historical pollution trends