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IMPROVING NEW MEXICO’S WATER MANAGEMENT - page 3 / 47

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We begin with a detailed overview of where New Mexico’s water is currently applied

and the economic aspects of that use. This review indicates that the vast majority of water is used

in agriculture, and that the state is dangerously dependent on groundwater pumping.

II. Profile of water use in New Mexico

New Mexico has five primary rivers. To a large extent the Canadian, Gila, Pecos, Rio

Grande, and San Juan rivers are the renewable sources of water in the state. This section reviews

the physical withdrawals and consumptive use on the major rivers and the economic value of

water for agriculture, municipal and environmental uses.

Diversions and Consumptive Use

A characteristic of water that is often misunderstood is the difference between diversion

and withdrawal or consumptive use. A user will divert water out of stream and apply it to some

use such as growing a crop. The crop actually evaporates less water than what is applied (the use

of water by plants is called evapotranspiration – a combination of evaporation from wet surfaces

and transpiration by the plant). Water that is evaporated or otherwise lost to the system is the

amount of consumptive use (consumptive use is also called withdrawal or depletion). We will

use consumptive use (CU) throughout the paper. The unused water or return flow seeps down

into the groundwater, and because shallow aquifers and rivers are usually connected

(conjunctive), the return flow will eventually make it back to the river. The return water then

becomes available for downstream diversion and use. Diversion, evaporation and return flow

occur for almost all uses except instream flows. Municipal water has a return flow (usually about

50%) through the sewer system. For some uses, the diversion is not so obvious. Users often

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