Hydro-Logic: Balancing Limited Water Supply with Increased Demand | green infographics | Scoop.it

The hydrological water year starts every autumn on 1 October and extends to the following 30 September. The available description from the USGS does not explain why this is the period considered, but there is some natural logic to the hydrological year: with the end of summer comes the (approximate) end of intense evaporation from reservoirs and the beginning of the seasons in which the net water balance in a watershed is generally positive. That is, in general, precipitation > evaporation.

Normally, from the beginning through about two-thirds of the water year, water is stored in the higher reaches of large watersheds as snowpack, which melts and runs off through the rest of the water year. Stream flows generally continue to drop from October through winter, but then rise significantly at the start of the melt season. That imbalance applies over a period longer than a single storm and for the whole watershed, not just on a random wet or dry day in one's own neighborhood.


One of the more interesting areas to observe the water year is the Colorado River Basin (CRB) in the southwestern US. The Colorado River has become so strictly regulated, in part because of gross over-allocation, over nearly a century of intensive use that it has become what I think is a consummate example of the coupled natural - human system...


Visit the link for a closer look at this detailed map of the CRB natural and engineered systems designed for National Geographic. Also, obtain more information regarding statistics on CRB flows and the status of reservoirs and other river operations, including links to various organizations and resources for further study...