Monday, October 15, 2007

Heron Lake water use basics

Heron Lake holds about 400,000 acre feet of water.

In a normal year Heron can get 96,200 net acre feet of water, the so-called "firm yield". If we get a very wet year, and the runoff is prolonged, we could theoretically get about twice that, based on the capacity of the Azotea Tunnel and the diversion system. Heron is not allowed to get more than 150% of the normal average during a 10-year period. A minimum amount of water must go downstream into the southern Colorado streams. If the snow in southern Colorado melts very quickly, we may get an intense but short diversion season, limiting the amount of water received by Heron.

Every year, the contractors -- cities, pueblos, or other governments that have paid for the water -- are entitled to take 96,200 a.f. Sometimes the water gets sold to the Feds for environmental purposes, i.e., minnow water. The 96,200 water is always taken by the contractors or purchasers.

When the City of Albuquerque gets its water plant running, they may spread out the timing of when they take their water, but they won't be taking any additional water.

The contractors have until Dec. 31 in theory, and until the following April in practice with the routine granting of waivers to take their water. If they don't take it they lose it. But, once they take it, and move it downstream, they incur the loss of water due to evaporation.

The Middle Rio Grande Conservancy District has about 22,000 acre feet and takes a good chunk of it in summer. Albuquerque has 48,200 a.f. and takes its water normally from November through March or April, as do most of the other contractors.

If Heron gets more than the firm yield in a given season, the lake gets to keep it and the lake goes up for the year.

If Heron gets less than the firm yield in a given season, the contractors still get to take their 96,200 a.f., and the lake goes down for the year -- as it did in 2003 and 2004.

I would think that the State Parks folks and Friends of Heron and El Vado Lakes, along with the Bureau of Reclamation, should have all the answers.


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