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Ground‐Water Quality Related to Irrigation with Imported Surface or Local Ground Water
Author(s) -
Nightingale H. I.,
Bianchi W. C.
Publication year - 1974
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1974.00472425000300040012x
Subject(s) - groundwater recharge , hydrology (agriculture) , groundwater , environmental science , irrigation , surface water , water quality , sampling (signal processing) , environmental engineering , geology , aquifer , geotechnical engineering , engineering , ecology , electrical engineering , filter (signal processing) , biology
Ground‐water quality in an arid irrigated area that imports high quality surface water was compared with an adjacent up‐gradient area that uses local pumped ground water. A large irrigation canal separates the two areas which are up‐gradient from the pumping depression of the Fresno‐Clovis, California metropolitan area, which is dependent on ground water. Intensive sampling (154 wells) was done in the fall of 1972 after it was shown by previous sampling that the ground‐water electrical conductivity (EC), NO 3 − , and Cl − content had not significantly changed since 1967. Diagrammatic distribution maps for ground‐water quality showed great variability. The Wilcoxon‐Mann‐Whitney nonparametric statistical tests showed the significance probabilities for EC, NO 3 − , and Cl − differences above and below the canal were 0.093, 0.114, and < 0.00006, respectively. The significance of these differences are determined by the reader or decision‐maker by his chosen error probability, the error risk he is willing to take in rejecting the null hypothesis of no difference when it is true. Areas of higher ground‐water NO 3 − and Cl − were generally related to soil drainage‐recharge and agricultural use. The use of local ground water without supplemental surface supplies above the canal has led to ground‐water EC, NO 3 − , and Cl − concentrations to be 9.5, 18.6, and 91.8% higher, respectively, than below the canal which uses mostly high quality surface water.