IWQ Index: A GIS-Integrated Technique to Assess Irrigation Water Quality

Abstract

The irrigation water quality and the associated hazards to soil characteristics and crop yield is often a complex phenomenon that involves the combined effect of many parameters. From a management point of view, it is sometimes necessary to analyze all related parameters as a combination rather than focusing on a single isolated parameter. With this objective in mind, a new GIS-integrated tool is proposed in this study to evaluate the quality of irrigation waters with regards to potential soil and crop problems. The proposed procedure is mainly an index method that utilizes five hazard groups: (a) salinity hazard, (b) infiltration and permeability hazard, (c) specific ion toxicity, (d) trace element toxicity; and, (e) miscellaneous impacts on sensitive crops. A linear combination of these groups is formulated to form the so-called IWQ index, which is a technique that could be used to classify irrigation waters with respect to three suitability classes. The proposed technique is applied to assess the irrigation water quality of the Simav Plain located in western Anatolia, Turkey. The Simav application is implemented by using a GIS database developed for the plain. Based on the results of this application, the general groundwater quality in the surfacial aquifer is found to be fairly good and the aquifer waters are mostly suitable for irrigation purposes.

Water Quality Assessment of Aflaj in the Mountains of Oman

“…Three categories -high, medium and low -were given to the three rating suitability (3, 2, 1), respectively (Appendices I, II, III). After the total value of the index was computed, a suitability analysis was done based on the three different categories of WQI: low (< 22), medium (22-37) and high (> 37) (Simsek & Gunduz, 2007). The detailed calculation of all five hazard categories and the WQI are summarized in Appendix IV.…”

“…Using the combined results of EC measurements and the SAR values, the analytical data plot on the EC-SAR diagram illustrates that most of the summer and winter water samples from the aflaj (Figure 3) fall in the field of C2-S1 (good: medium salinity/low sodium hazards) suitability based on the EC and SAR classification of irrigation water (Appendix V). These categories of water quality can be used for irrigation of most crops and majority of soils (Richard, 1954;Simsek & Gunduz, 2007). …”

“…Appendix II: Classification for infiltration and permeability hazard (Simsek & Gunduz, 2007) Appendix III: Classification for trace element toxicity (Simsek & Gunduz, 2007) Parameter (mg/l) Rating …”

“…The presence of excessive amounts of ions in irrigation water affects soil's physical and chemical properties, reduce soil productivity, create crop toxicity and eventually reduce yields (Kraiem et al, 2014;Nag, 2014;Varol & Davraz, 2015). Major water quality problems for irrigation are salinity, sodicity and alkalinity (Simsek & Gunduz, 2007;Sadashivaiah et al, 2008;Nazzal et al, 2014). An appropriate assessment of water for irrigation requires the determination of of physical, chemical and biological parameters that are greatly influenced by geological formations and anthropogenic activities (Sarath Prasanth et al, 2012;Al-Khashman & Jaradat, 2014;Al-Harbi et al, 2014) and directly related to the classifying of water quality (Saber et al, 2014;Aly, 2014;Aly et al, 2014).…”

“…Several quality indices can be used to assess the suitability of water for irrigation; the most commonly used are salinity hazards, percent sodium (% Na), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), soluble sodium percentage (SSP), residual sodium bicarbonate RSBC), permeability index (PI), potential salinity (PS), Kelley's index (KI) and magnesium hazard (MH) (Tatawat & Chandel, 2008;Sarath Prasanth et al, 2012;Al-Harbi et al, 2014;Nag, 2014). Water quality index (WQI) also provides a simple and concise method for assessing the water quality by integrating the water quality variables into one single number depending on several quality variables: salinity hazard, infiltration or permeability hazard, specific ion toxicity, trace element toxicity, and various miscellaneous effects to susceptible crops (Lou & Han, 2007;Simsek & Gunduz, 2007;Tatawat & Chandel, 2008;Mohammed Muthanna, 2011;Al-Bahrani et al, 2012;Adhikari et al, 2013;Aly et al, 2014).…”