Flood vs. Drip Irrigation; Which is better?

New Mexico State University
News Center

Date: 2009-10-15
Writer: Jane Moorman

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 conservation 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 head.

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.

The NRCS has responded!  Roger Ford, State Conservation Engineer, sent Roger Ford, State Conservation Engineerus this e-mail responding to our request for comment.

Send us your comments.  We'll post them here.

We repeatedly requested comments on these papers from NRCS officials both here in Taos and in the state office in Albuquerque.  We were referred to the NRCS web site, where we found this general observation:

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 EQIP Program page.  Programs listed include concrete lining of irrigation ditches (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 of acequias and groundwater levels on riparian vegetation, evapotranspiration,and restoration, being conducted at the NMSU Sustainable Agricultural Science Center in Alcalde.  This research will explore the following hypothesis:

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 are available.

Here are two more papers of interest from NRCS: