New Mexico is the nation’s fifth largest state in area at 121,600 mi2 after Alaska, Texas, California, and Montana and yet ranks 36th in total popu la tion at 1,980,000 in 2008. New Mexico ranks sixth from the bottom in popu la tion density at 16.4 persons/mi2 (U.S. Census Bureau, 2010). One reason for the sparse popu la tion is the limited water resources in the state. As will be discussed in this chapter, the water resources in all watersheds are fully used at present and in fact in most basins water is being used more rapidly than it is being replenished. This chapter summar izes the surface and ground water resources of the state, and includes a discussion of the prin cipal water quality challenges in each basin. Because water is so im port ant to the state’s eco nomic institutions and social struc tures it has been intensively studied. There is a large amount of data avail able in the form of data bases such as those maintained by the U.S. Geological Survey (USGS) and U.S. Environmental Protection Agency (EPA), state and local agencies, as well as technical reports, books and monographs, and pub lications in research journals. A quantitative summary and in ter pretation of this in forma tion would fill an encyclope dia but even then would be incomplete and dated the day it was published. Thus, this chapter presents a summary of the resources and issues, and provides the rel ev ant con text, explanation, and key ref er ences to pri mary sources for further information. In this discussion it is im port ant to clarify a couple of terms. Consumptive use refers to water that is withdrawn from a source (i.e., stream, lake, or aquifer) and is not returned to any body of water. Basically, this is water that is lost to evaporation and by other means such as water incorp or ated into harvested crops. Diversion de scribes the total amount of water that is withdrawn from a source. It is also com monly referred to as withdrawals. An impressive stat ist ic often cited is that electric power generation in the U.S. accounts for about 40 percent of the total diversion of water in the U.S. (DOE, 2006). However, this water is used for cooling and 97 percent of it is returned to a lake, river, or the ocean. Consumptive use is the
dif fer ence between the volume of water diverted and that returned to the receiving body of water. The power industry’s consumptive use is only 3 percent of the total amount diverted. Thus, Longworth et al. (2008) have estim ated surface and ground water withdrawals throughout the state of New Mexico, but comparatively little in forma tion is avail able on consumptive use. Depletions can refer to either con sumptive use or ground water withdrawals. In this chapter depletion refers to con sumptive use. There are six river basins in New Mexico (Figure 3.1). Within these basins are several closed basins; topographic depressions in which surface water flows to the center of the basin and is lost to evaporation and infiltration so that there is no surface runoff. The major closed basins are the Estancia Basin, San Au gustin Basin, Jornada del Muerto, Tularosa Basin, Salt Basin, and Mimbres Basin. Though there is no surface runoff from these basins, many of them have or are suspected to have subsurface flow with adjoining basins. For example, the Estancia Basin is believed to con trib ute ground water flow to the adjoining Tularosa Basin. Total water withdrawals in New Mexico in 2005 are summar ized in Table 3.1 (Longworth et al., 2008). This data is the source of the often cited figure that total water use in the state of New Mexico is 4,000,000 AF/yr. In addition to the surface water basins, the Office of the New Mexico State Engineer (OSE) has identified 37 ground water basins. These are identified for administrative purposes and are based both on polit ical bound ar ies and hydrogeo logic cri teria. Frequent ref er ence is made to these bound ar ies in planning and administrative docu ments, as well as water resource investigations. Issues common to most of the basins include:
1. Total water uses exceed total legal enti tle ments for the various sources of supply.