Saturday, September 27, 2008

Recap:Water: The High Plains Aquifer

Here is a link to my erstwhile blog article on water depletion in the High Plains/Ogallala aquifer.

The High Plains aquifer underlies one of the most productive agricultural regions in the US. This region is semi-arid and does not get much precipitation, therefore most of the water used for irrigation is drawn from wells. Ground water levels here have been dropping and I thought of doing a zeroth order analysis of how many years will the water in the aquifer last. I used water level change data from USGS. According to USGS, there has been no major change in area under irrigation from 1988-2002. This report also points out that the total change in ground water storage from 1988-2000 was 47 million acre-feet and that the total ground water storage (estimated) in 2000 was 2970 million acre-feet. If we assume that ~30% of this water is recoverable, this gives us an approximate lifetime of 230 years (assuming that the irrigated acreage does not increase). However, the irrigated acreage did increase from 2002-2003, and the rates of depletion are approximately twice their value from 1988-2002. A map showing generalized water-level changes in the aquifer from 2002-03 are shown in the report. As expected, there is a lot of heterogeneity in the way water-levels dropped. Parts of central and south High Plains underwent more drastic water-level changes compared to their northern counterparts. Accordingly, the area-weighted water-level changes per state were more pronounced in Kansas, New Mexico, Oklahoma, and Texas compared to Colorado and Nebraska. Therefore, even if the water might still be around for another 2 centuries, parts of the High Plains might be facing depleted ground water levels sometime soon. These water-level changes might have important implications for US food supply.

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