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Title: Empirical evidence for a recent slowdown in irrigation-induced cooling

Abstract

Understanding the influence of past land use changes on climate is needed to improve regional projections of future climate change and inform debates about the tradeoffs associated with land use decisions. The effects of rapid expansion of irrigated area in the 20th century has remained unclear relative to other land use changes, such as urbanization, that affected a similar total land area. Using spatial and temporal variations in temperature and irrigation extent observed in California, we show that irrigation expansion has had a large cooling effect on summertime average daily daytime temperatures (-0.15 to -0.25 C.decade{sup -1}), which corresponds to a cooling estimated at -2.0 - -3.3 C since the introduction of irrigation practice. Irrigation has negligible effects on nighttime temperatures, leading to a net cooling effect of irrigation on climate (-0.06 to -0.19 C.decade{sup -1}). Stabilization of irrigated area has occurred in California since 1980 and is expected in the near future for most irrigated regions. The suppression of past human-induced greenhouse warming by increased irrigation is therefore likely to slow in the future, and a potential decrease in irrigation may even contribute to a more rapid warming. Changes in irrigation alone are not expected to influence broadscale temperatures,more » but they may introduce large uncertainties in climate projections for irrigated agricultural regions, which provide roughly 40% of global food production.« less

Authors:
;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
940480
Report Number(s):
UCRL-JRNL-229604
TRN: US200824%%43
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: Proceedings of the National Academy of Sciences, vol. 104, no. 34, August 21, 2007, pp. 13582-13587; Journal Volume: 104; Journal Issue: 34
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; CALIFORNIA; CLIMATES; FOOD; GREENHOUSE GASES; IRRIGATION; LAND USE; PRODUCTION; STABILIZATION

Citation Formats

Bonfils, C, and Lobell, D. Empirical evidence for a recent slowdown in irrigation-induced cooling. United States: N. p., 2007. Web. doi:10.1073/pnas.0700144104.
Bonfils, C, & Lobell, D. Empirical evidence for a recent slowdown in irrigation-induced cooling. United States. doi:10.1073/pnas.0700144104.
Bonfils, C, and Lobell, D. Fri . "Empirical evidence for a recent slowdown in irrigation-induced cooling". United States. doi:10.1073/pnas.0700144104. https://www.osti.gov/servlets/purl/940480.
@article{osti_940480,
title = {Empirical evidence for a recent slowdown in irrigation-induced cooling},
author = {Bonfils, C and Lobell, D},
abstractNote = {Understanding the influence of past land use changes on climate is needed to improve regional projections of future climate change and inform debates about the tradeoffs associated with land use decisions. The effects of rapid expansion of irrigated area in the 20th century has remained unclear relative to other land use changes, such as urbanization, that affected a similar total land area. Using spatial and temporal variations in temperature and irrigation extent observed in California, we show that irrigation expansion has had a large cooling effect on summertime average daily daytime temperatures (-0.15 to -0.25 C.decade{sup -1}), which corresponds to a cooling estimated at -2.0 - -3.3 C since the introduction of irrigation practice. Irrigation has negligible effects on nighttime temperatures, leading to a net cooling effect of irrigation on climate (-0.06 to -0.19 C.decade{sup -1}). Stabilization of irrigated area has occurred in California since 1980 and is expected in the near future for most irrigated regions. The suppression of past human-induced greenhouse warming by increased irrigation is therefore likely to slow in the future, and a potential decrease in irrigation may even contribute to a more rapid warming. Changes in irrigation alone are not expected to influence broadscale temperatures, but they may introduce large uncertainties in climate projections for irrigated agricultural regions, which provide roughly 40% of global food production.},
doi = {10.1073/pnas.0700144104},
journal = {Proceedings of the National Academy of Sciences, vol. 104, no. 34, August 21, 2007, pp. 13582-13587},
number = 34,
volume = 104,
place = {United States},
year = {Fri Jan 19 00:00:00 EST 2007},
month = {Fri Jan 19 00:00:00 EST 2007}
}
  • Saline cooling tower water (CTW) from the Sherburne County electrical power plant in Minnesota is being considered as an irrigation water source on surrounding crop lands. This study was undertaken to determine composition of drainage waters, leaching fractions (LF), and quality of the underlying aquifer (10-12 m) as affected by irrigation with CTW at two rates under three cropping systems. In a 3-yr field study (1979-1981), alfalfa (Medicago sativa L.), corn (Zea mays L.), and fallow plots were irrigated at rates that replaced net water deficits (I/sub 1/) and twice the net water deficits (I/sub 2/) in the cropped areas.more » The soil at this site was a Hubbard loamy sand (Udorthentic Haploboroll). Lysimeters, 57 cm in diam, were buried 150 cm below the plots to monitor the composition of the drainage waters and to determine the LF. Wells were installed in all plots to monitor deep movement of the CTW salts into the aquifer. Application of CTW increased the concentration of Ca and SO/sub 4/ in the drainage waters. Salt concentrations were generally higher under alfalfa than corn and fallow, reflecting its higher water requirement. Drainage waters were undersaturated with respect to gypsum; thus, SO/sub 4/ added from the irrigation water stayed in solution. The LF under the I/sub 2/ rate averaged 0.58. The LF under the alfalfa and corn (I/sub 1/ rate) averaged 0.34 and 0.38, respectively. The LFs under the I/sub 1/ rate were higher than anticipated. Salt concentrations in the aquifer increased greatly over the 3 yr. Sulfate concentrations peaked at 6.4 mmol L/sup -1/ in 1981, over 20 times greater than background levels and higher than US Environmental Protection Agency drinking water standards.« less
  • Ozone is an oxidizing agent possessing potent in vitro microbicidal capacity. This study was designed to address the extent to which irrigation of the contaminated abdominal cavity using a saline solution primed with ozone is effective in reducing morbidity and mortality. Gelatin capsules containing different quantities of a premixed slurry of filtered human fecal material were implanted in the peritoneal cavities of a preliminary series of rats. Three inocula concentrations were selected for later experiments, based upon their ability to produce morbid consequences: (1) high (100% 1-day mortality), (2) medium (70% 3-day mortality, 100% abscess rate in survivors), and (3)more » low (100% 10-day survival, 100% abscess rate). Fecal and abscess bacteriology were similar in all rats. The peritoneal cavities of 240 rats then underwent fecal-capsule implantation (three groups of 80 rats/inoculum concentration). At celiotomy 4 hours later, equal numbers of rats from each group were randomly assigned to one of four protocols: (1) no irrigation, (2) normal saline irrigation, (3) saline-cephalothin irrigation, and (4) ozonated saline irrigation. Each treatment lasted 5 minutes, using 100 ml of irrigation fluid. Mortality was significantly reduced when, in lieu of no irrigation, any of the irrigation solutions were used. Additionally, ozonated saline statistically proved the most effective irrigating solution for reducing abscess formation in survivors.« less
  • The Department of the Interior has embarked on a series of reconnaissance-level investigations throughout the Western US to identify, evaluate, and respond to irrigation-induced water quality problems. A series of water, sediment, and biological samples are being analyzed for 17 inorganic constituents and a number of pesticides. Nineteen studies in 13 states have been undertaken. Seven have been completed to date. Results of the seven studies that have been completed are presented and compared to baselines, standards, criteria, and other guidelines helpful for assessing the potential of observed constituent concentrations in water, bottom sediment, and biota, to result in physiologicalmore » harm to fish, wildlife, or humans. Several observations about the nature of irrigation-induced contamination problems were made based upon the evaluation process described. Selenium was most commonly found at elevated concentrations in wetland ecological systems receiving irrigation drainage water. Concentrations of analytes varied widely on a spatial basis in all environmental media sampled, suggesting that irrigation-induced contamination problems are likely to be very site-specific. Closed watersheds are most likely to exhibit symptoms of irrigation-induced contamination. Certain hydrologic and geochemical characteristics can serve as indicators of potential problems with irrigation drainage. These initial results indicate that a new environmental problem of major proportions does not exist, but that some localized problems of significant magnitude do exist and should be addressed. 11 refs., 1 fig.« less
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