Salt balance of moderately saline-alkaline rangeland soil and runoff water quality from rainfall simulation studies near Moab, Utah U.S.A.

Authors: ARSLAN, AWADIS - UNIVERSITY OF NEVADA; Weltz, Mark; Nouwakpo, Sayjro

Submitted to: Journal of Geological Resource and Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2020
Publication Date: 2/28/2020
Citation: Arslan, A., Weltz, M.A., Nouwakpo, S.K. 2020. Salt balance of moderately saline-alkaline rangeland soil and runoff water quality from rainfall simulation studies near Moab, Utah U.S.A. Journal of Geological Resource and Engineering. 8(1):1-19. https://doi.org/10.17265/2328-2193/2020.01.001.
DOI: https://doi.org/10.17265/2328-2193/2020.01.001

Interpretive Summary: A Walnut Gulch rainfall simulator was used to determine runoff water quality and salt balance of a salt desert rangeland plant community on a Loam saline-alkaline soil containing 0.27% of gypsum near Moab, Utah. Four rainfall intensities corresponding to 2, 10, 25 and 50-year storm return intervals were applied to dry soil. During each rainfall simulation, time-stamped runoff samples were collected for the determination of the concentration of cations and anions. Soil water and solute content by depth increments were determined before and after simulations. All correlation coefficients between the applied simulation water (l) and the amounts of Cl-, SO42-, NO3- and sum of anions in runoff water (mmolc/plot) were positive. The Ca2+, Mg2+, Na+, K+ and sum of cations ranged between 0.783 and 0.983. We concluded from the data analysis that: 1) The amounts of cations and anions in simulation water and in runoff water represent less than 1% of sum of the soil soluble content measured before rainfall simulation. 2) The CEC contained about 2.5 times the sum of cation in saturated extract. 3) The very small amount of gypsum in the soil contained 50% the sum of saturated extract cations and anions. This means that special attention should be paid to CEC and gypsum content in the management of such soils. Moreover, when modeling runoff and water quality from soils with these properties the modelers must include subroutines using physical chemistry approaches or suitable functions containing gypsum and CEC of the soil for accurate prediction of runoff water quality and/or changes in soil proper-ties after rainfall events.

Technical Abstract: A Walnut Gulch rainfall simulator was used to determine runoff water quality and salt balance of a Sandy Loam moderately saline-alkaline site containing 0.27% of gypsum near Moab, Utah. Four rainfall intensities corresponding to 2, 10, 25 and 50-year storm return intervals were applied to dry soil. During each rainfall simulation, time-stamped runoff samples were also collected for the determination of ions concentration. Soil water and solute content by depth increments were determined before and after simulations. All correlation coefficients between the applied simulation water and the amounts of Cl-, SO4 2-, NO3- and sum of anions in runoff water were positive and ranged between 0.922 and 0.999. The correlation coefficients for Ca2+, Mg2+, Na+, K+ and sum of cations ranged between 0.783 and 0.983. We concluded from the data analysis that: (1) The amounts of ions in simulation water and in runoff water represent less than 1% of sum of the soil soluble content before rainfall simulation. (2) The CEC contained about 250% the sum of cation in saturated extract. (3) The very small amount of gypsum in the soil contained 50% the sum of saturated extract ions. This means that special attention should be paid to CEC and gypsum content in the management of such soils. Moreover, when modeling runoff and water quality from soils with these properties the modelers must include suitable subroutines considering gypsum and CEC of the soil for accurate prediction of runoff water quality.