There is a
cascade of thresholds through which we are moving, as use of freshwater and lack of environmental controls increases hydrological concerns in many regions and ecosystems. We know water is more precious than gold. Simply ask the previous victims of great water shortages in the Sahel or even in the Kansas Dust Bowl.
Humans have created chaos by robbing water bodies from the loss of the Aral Sea (which we have documented here) to the profligate use of water to maintain Australian or Californian lawns. The consequences are unfortunately irreversible. The scarcity of water is becoming frightening as water stress affects not simply the drought areas but all of us.
Answers for the human species often involve the global warming problem, as the water evaporates, but this can create more rainfall in a few areas. Climate change separately brings in some desertification and loss of river volumes, as people remove that flow in various ways to compensate for lack of water elsewhere. Pollution, even including fracking, is responsible for huge losses of drinkable water, disregarding the effects of our waste on the oceans (which is another kettle of fish!) and that effect on atmospheric evaporation and rainfall.
Elsewhere, groundwater extraction in the Hai River Basin in China is infamous as >50% of the sustainable yield is removed from the highly polluted waters. Remaining in that area, hydropower is both beneficial and injurious to water supply. On the one hand the reservoir situation provides a supply for drinking and/or recreation. On the other, downstream sites lose biodiversity (see Water Politics below), water, groundwater, agricultural diversity and are subject to increased pollution because of the lack of flow. One US and a few other examples were noted in this California-based article.
The whole point can be abbreviated to intervention requirements. Water belongs to all of us, including natural communities that are being lost because of the lack of
water boundary and environmental flow requirement. The classic Environmental Impact Assessment has lost some of its importance as commercial interests attempt to hijack the idea and sell it as their own requirements from the system. The requirement is from the whole ecosystem, and while profit is important, it has very often become the all-powerful motivation. Environments are, or should be, some shade of
green, brown or even pink. We can take one example from the 20th century where Metro-Manila achieved some relief from ridiculous shortages of water supply and waste disposal over a twenty-year period. This quirky report is full and has no modern outlook, but does try to point out routes that anyone can take to achieve a similar urban result in almost any country, but especially where Environmental Impact Assessment is a creature that is rarely seen. More detail on recent water effects on environment with comments by Charles Vorosmarty and Ban Ki-Moon can be found in Water Politics.