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Regional
water planning is informed decision-making about present and
future use of our regional water resources (1). The planning
process includes collection of data and information. What are
the facts upon which we will base our decisions? Planning also
includes identification of the region's goals and priorities,
such as policies related to growth and environmental protection.
Finally, planning encompasses development of strategies to meet
those goals as well as implementation.
Southwestern
New Mexico has completed its regional water plan as part of
the statewide
water planning process. View PDF's of the Southwest New
Mexico Regional Water Plan here.
The recently-released supplement
to Silver City's 40-year water plan demonstrates that
the Gila Group Aquifer has sufficient water to meet the town's
estimated future needs without addition of 10,000 acre-feet
of Gila River water promised to the state under the Arizona
Water Settlements Act. Conducted by Balleau Groundwater Inc.,
the groundwater modeling assessment shows that the regional
aquifer known as the Mimbres-Mangas Trench has approximately
15.2 million acre-feet of groundwater, with 15,900 acre-feet
per year of recharge, enough to sustain the area for hundreds
of years.
The
report's author, Dave Romero, stated at a recent public meeting
on the report that the town's permitted use could be exceeded
within the next 16 - 38 years depending upon population growth
rate (1.2 vs. 2.9 percent per year). The town currently uses
about 2,800 acre-feet per year of water and has water rights
(permitted use) of 4,567 acre-feet per year. Romero recommends
that the town should start to acquire additional water rights
now to make sure that its diversion does not exceed its permitted
use. The modeling also predicts that the yield from Silver
City's well fields could start to decline in 30 years at the
high population growth projection thus requiring drilling
replacement wells or deepening existing ones.
Despite
what the state and town boosters would have us believe, Romero
admits that it's highly unlikely that our area will experience
a 2.9 percent annual growth rate. He rationalized using such
a large number as a planning exercise. However, the future
of the Gila River is at the mercy of these planning estimates
as the NM Interstate Stream Commission (ISC) moves ahead with
efforts to divert as much as 10,000 acre-feet of water per
year from the Gila River for Silver City's water supply under
the Arizona Water Settlements Act. The idea that's been discussed
by the ISC is to divert water from the river when flows are
above specified monthly diversion parameters, pipe the water
to a 50,000 acre-foot impoundment on Mangas Creek (about 25
times the size of Bill Evans Lake), and then pump the water
over the Continental Divide to the Silver City well fields
to recharge the aquifer. Not accounting for evaporation and
other water losses from the system, the 8,000 acre-feet per
year yield discussed in the Southwest New Mexico Regional
Water Plan seems like a drop in the bucket compared to the
15.2 million acre-feet of water held in that aquifer. All
of this assumes that 10,000 acre-feet per year can be taken
from the Gila. Factoring in the drought and potential impacts
to endangered species, the viability of the project is highly
questionable.
Moreover,
this project is too expensive. The Gila Conservation Coalition's economic analysis,
produced by economic consulting firm, ECONorthwest, shows
that a Gila River diversion would cost 16 times more than
acquiring additional water rights and drilling new wells and
could impose an additional $268 million in cost on the tax
payer.
LET'S
HAVE OUR CAKE AND EAT IT TOO
The
Gila River is the last free-flowing river in New Mexico and
maintaining its relatively natural flow regime is critical
to its ecological values. ECONorthwest estimated that if the
residents of New Mexico hold values for the Gila River's ecological
attributes similar to those found in studies regarding similar
natural resource amenities, the economic costs due to ecological
impacts of a Gila River diversion could be as much as $218
million. By choosing to use groundwater rather than surface
water, Silver City can meet future water demand at much lower
cost while also allowing the Gila River to remain a riparian
jewel of the southwest.
(1) Adapted from "Taking
Charge of our Water Destiny: A Water Management Policy Guide
for New Mexico in the 21st Century," by Alletta Belin,
Consuelo Bokum, Frank Titus for 1000 Friends of New Mexico.
2002. |
