pump groundwater as their source of water. To the extent that the aquifers are conjunctive to the
river,1 the surface system will replenish the deficit created in aquifers and surface flows will be
The distinction between diversion, evaporation and return flow is significant in that all
affect the river in different ways. Diversion has an immediate effect of reducing surface flows
but the extracted volume is partially replaced by return flow. It is often common to have more
total diversions than native water in the river. Return flows are usually of higher salinity than the
river so as water is diverted and returned repeatedly, salinity in the river increases. Evaporation
is a withdrawal of water from the river.
The following five sets of tables indicate by sector (a) surface and groundwater
diversions, (b) return flow, and (c) consumptive use in major river basins of New Mexico.
1 The relationship between surface and groundwater is often extremely complex. Some groundwater withdrawals are never replaced by the river and are ”mined”. Other river-aquifer connections involve considerable time lags between when the water is pumped and when the pumping affects surface flows.