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Patterns and associations between dominant crop productions and water quality in an irrigated watershed

Nouwakpo, S.K. and Bjorneberg, D.L. and Rogers, C.W. (2023) Patterns and associations between dominant crop productions and water quality in an irrigated watershed. Journal of Soil and Water Conservation. 78(6):466-478. 1 November 2023.

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Irrigation consumes the largest share of freshwater resources but is a necessary practice to boost agricultural output to meet increasing global demand for food and fiber. Irrigation not only impacts water quantity but can also degrade water quality. Research efforts have explored various aspects of irrigation efficiency and irrigated crop productivity, but few studies have examined how different crops collectively modulate water utilization and water quality at the watershed scale. In this study long-term water quantity and quality monitoring data collected as part of the Conservation Effect Assessment Project (CEAP) combined with crop and evapotranspiration (ET) modeling products were used to elucidate relationships between crop and water processes in an irrigated watershed. We use a correlational approach to build relationships between water quantity and quality metrics and the fractional volumes of ET associated with major crops in the Twin Falls Canal Company irrigation tract. Results suggest that sub-watershed size and subsurface flow contribution in drainage tunnels influenced hydrologic patterns observed and led to 2 distinct groups. Group 1 sub-watersheds were large, typically included subsurface drain tunnels and had high return flow volumes and low sediment concentration while group 2 sub-watersheds were smaller in size, had low return flow volumes and high sediment concentration. Irrigation return flow volume normalized by sub-watershed area was positively associated with ET fractions of potato (Solanum tuberosum) in group 1 during the spring and summer months. Spring sediment loss per return flow volume showed a negative association with ET fractions of sugar beet and combined alfalfa (Medicago sativa) and pasture crops in group 2. A negative association was found between phosphorus (P) load per return flow volume and ET fractions of alfalfa / pasture, corn (Zea mays), dry beans (Phaseolus vulgaris), and sugar beet (Beta vulgaris) across sub-watershed groups. Nitrate (NO3-N) load per return flow volume was negatively associated with potato and corn ET fractions in group 1 especially during the spring and fall month but positively associated with dry beans over the irrigation season. While direct cause and effect were not established between crops and water quantity and quality, results from this study provide valuable information on management factors associated with various crop production systems that may control observed hydrologic response. Example of factors considered in explaining some of the observed patterns include early germination and ground coverage, tight control on soil water content, and the erosion attenuation effect of sedimentation ponds.

Item Type: Article
NWISRL Publication Number: 1784
Subjects: Water > Evapotranspiration
Water > Water quality
Depositing User: Users 11 not found.
Date Deposited: 09 May 2024 16:05
Last Modified: 09 May 2024 16:05
Item ID: 1827