I have lately been reading reports from the recently finished World Water Week 2007 held in Stockholm, Sweden. The most interesting (and best written) report is on water scarcity(pdf).
The article does a very good job of pointing out that there are different types of water scarcity. One important distinction is between blue water scarcity and green water scarcity. Blue water is that in rivers and lakes and aquifers, whereas green water is that retained in the soil. Blue water is the water used directly - drinking, washing, etc, Green water is important for crop production.
Another very important distinction is between real and apparent water scarcity. Real water scarcity is due to lack of rainfall or to having too many people sharing the same resource. Apparent water scarcity is where there is sufficient water but the water gets wasted due to inefficiency and losses.
The importance of these distinctions is that different types of water scarcity require different solutions. For example, apparent green water scarcity requires soil conservation measures to reduce losses due to runoff and poor infiltration. Whereas, apparent blue water scarcity requires reduces system leaks and reducing wasteful water usage.
Notice all this means improving planning and prior determination of the causes of water problems in order to have effective conservation measures.
Finally, one of the most important recommendations of the report is:
When taking concrete policy steps, decision makers should first focus on managing demand – efforts to increase supply should be secondary to that.