vs. Drip Irrigation; Which is better?
We have recently come across an article published in the Proceedings of the
National Academy of
Science of the United States of America, entitled Water
in irrigation can increase water use, that addresses this
question, and reaches the following conclusion:
This article presents results of an
integrated basin-scale analysis linking biophysical, hydrologic,
agronomic, economic, policy, and institutional dimensions of the Upper
Rio Grande Basin of North America. It analyzes a series of water
conservation policies for their effect on water used in irrigation and
on water conserved. In contrast to widely-held beliefs, our results
show that water conservation subsidies are unlikely to reduce water use
under conditions that occur in many river basins. Adoption of more
efficient irrigation technologies reduces valuable return flows and
limits aquifer recharge. Policies aimed at reducing water applications
can actually increase water depletions. Achieving real water savings
requires designing institutional, technical, and accounting measures
that accurately track and economically reward reduced water depletions.
Conservation programs that target reduced water diversions or
applications provide no guarantee of saving water.
This paper was prepared by Frank A. Ward of the Department of
Agricultural Economics and Agricultural Business, New Mexico State
University, Las Cruces, NM 88003 and Manuel Pulido-Velazquez of the
Department of Hydraulic and Environmental Engineering–Institute of
Water and Environmental Engineering, Universidad Polite´ cnica de
Valencia, Cami de Vera s/n 46120 Valencia, Spain. It was edited
by Partha Sarathi Dasgupta, University of Cambridge, Cambridge, United
Kingdom, and approved September 23, 2008.
The paper, based on research conducted on the Upper Rio Grande,
specifically compares water use and cost per unit of agricultural
output for flood vs. drip irrigation. It concludes that not only
is the cost per unit greater for drip irrigation, not a surprising
finding, but that for most crops water use is greater for drip
irrigation as well, a finding that stands conventional wisdom on its
Subsequently, a student at NMSU has posted a paper on his blog, Tragedy
of the Commons Dilemma and Consumptive Water Use Within the NRCS
Environmental Quality Incentives Program. While not nearly as
carefully researched (or well written!), this addendum builds on the
earlier work, and points specifically at the NRCS EQIP program as a
major culprit in the misguided application of public funds, intended to
conserve water but actually having the opposite effect.
We repeatedly requested comments on these papers from NRCS
officials both here in Taos and in the state office in
were referred to the NRCS
web site, where we found this
Subsurface Drip Irrigation (SDI) is one of
several types of Microirrigation (Conservation Practice Standard 441).
It is a planned irrigation system in which water is applied directly to
the root zone of plants by means of applicators (E.g. orifices,
emitters, and porous tubing) placed below the ground surface. It is
operated under low pressure. It is one of the more advanced irrigation
methods in use today. It is potentially more efficient than flood or
sprinkler irrigation, due, in large part to reduced evaporation.
Digging a little deeper, we found the NRCS
page. Programs listed include concrete lining of irrigation
(3), and underground piping for transport of irrigation water
(15). Whether intentionally or not, all of these projects reduce
infiltration of groundwater into the aquifer, and increase the flow of
water back to the Rio Grande and downstream to support real estate
developments in Santa Fe and Albuquerque.
A new study is currently underway, Effects
acequias and groundwater levels on riparian vegetation,
evapotranspiration,and restoration, being conducted at the NMSU Sustainable
Science Center in Alcalde. This research will explore the
Acequias create localized areas where
restoration efforts are highly effective and are occurring naturally as
a result of the elevated water tables from acequia seepage.
We will follow this research, and report results on this page as they