Spatiotemporal variations of hydrochemical characteristics of irrigation water: a case study of the Lower Rio Grande Valley, USA

Abstract

Hydrochemical characteristics of irrigation water and their spatiotemporal variations can provide critical information for ensuring healthy crop growth and determining the best water management practices. The Lower Rio Grande Valley (LRGV) is heavily dependent upon ditch irrigation to deliver water from the Rio Grande River to support its staple crop production. To date, no studies have been conducted to quantify the water quality and its variations along the distribution system. This research measured water quality parameters at seven sites in LRGV irrigation water in 2021. Chemical indices including salinity hazard (SH), sodium adsorption ratio (SAR), sodium percentage (Na%), residual sodium carbonate (RSC), magnesium hazard (MH), Kelly's Ratio (KR), and permeability index (PI) were calculated. Classification diagrams were prepared. Results revealed the locations that had doubtful water for irrigation use and more problematic water quality index levels. June and August had the highest index levels, which may have been attributable to the large rainfall events in May and July. The SH, Na%, KR, and MH indices exceeded recommended levels. ANOVA analyses showed significant temporal variations in SAR, RSC, MH, KR, and PI. These findings indicate the importance of incorporating water quality spatiotemporal variation information in routine irrigation planning and management. HIGHLIGHTS Irrigation water quality varied from permissible to doubtful for irrigation use depending on the location and time of the samples collected.; Significant temporal variations in the water quality were identified.;

Keywords

• agriculture
• chemical indices
• crops
• rio grande river
• water classification diagrams
• water quality