Location: Water Quality and Ecology ResearchTitle: Representation of solid and nutrient concentrations in irrigation water from tailwater recovery systems by surface water grab samples Author
Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2017
Publication Date: N/A
Citation: N/A Interpretive Summary: Conservation practices such as tailwater recovery systems serve as alternative sources of irrigation water for farmers facing water deficits for their crops. A study was conducted to determine whether water samples collected at a single place and point in time would be representative of irrigation water quality found in tailwater recovery systems. Results showed no difference in sediment and nutrient concentrations between water collected in a single grab sample versus actual irrigation water being pumped onto fields. This study provides important evidence toward proper sampling to determine more accurate measurements of irrigation water quality in tailwater recovery systems.
Technical Abstract: Tailwater recovery (TWR) systems are being implemented on agricultural landscapes to create an additional source of irrigation water. Existing studies have sampled TWR systems using grab samples; however, the applicability of solids and nutrient concentrations in these samples to water being irrigated from TWR systems has yet to be investigated. This is important if research using grab samples is used to quantify the application of solids and nutrients back onto the agricultural landscape. In order to test whether grab samples are representative of water pumped from TWR systems for irrigation use, this study compared concentrations of total suspended solids (TSS), total P (TP), total N (TN), total Kjeldahl N (TKN), nitrate-nitrite (NO3-NO2-) and ammonium (NH4+). Grab samples were collected simultaneously from the surface water and from their respective outflow of irrigation infrastructure in six TWR systems in the Lower Mississippi Alluvial Valley. Comparison of 14 irrigation events showed TSS, TP, TN, TKN, NO3-NO2- and NH4+ did not differ between surface water grab samples and irrigation water samples. No differences were found for TN, TP, NH4+, and TKN across sites, however, differences between sites did exist for TSS and NO3-NO2-. This research suggests surface water grab samples from TWR systems represent the solid and nutrient concentrations being irrigated at that moment of time.