Artificial rainfall tests, soil moisture profiles and geoelectrical investigations for the estimation of recharge rates in a semi-arid area (Jordanian Yarmouk River Basin)

• Published in: Environmental earth sciences Vol. 73; no. 10; pp. 6677 - 6689
• Main Authors: Al Qudah, K., Abu-Jaber, N., Jaradat, R., Awawdeh, M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2015; Springer Nature B.V
• Subjects: Arid environments; Biogeosciences; Climatic data; Earth and Environmental Science; Earth Sciences; Environmental Science and Engineering; Evaporation; Excess water; Field capacity; Geochemistry; Geology; Groundwater recharge; Hydrology/Water Resources; Moisture; Moisture content; Moisture profiles; Original Article; Rain; Rainfall; River basins; Rivers; Runoff; Soil moisture; Soil profiles; Soil water; Soils; Terrestrial Pollution; Wilting; Wilting point; Jordan (country); Jordan, Yarmouk R; Geoelectrical investigations; Sprinkler tests; Recharge; Jordan; Soil moisture; Yarmouk Basin
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-014-3889-y

To overcome the limitations posed by the limited relevant data for recharge estimation in the Jordanian Yarmouk River basin, a mass balance methodology is developed which is simple and may be easily applied to other arid and semi-arid landscapes. This is done by integrating available climatic data with new rain–runoff relationship data, as measured using a specially designed and built artificial rainfall simulator, and changing soil moisture profiles through the hydrological year, as measured in the field. The amount of moisture in the soil after rainfall events changes as a result of both evaporation and of drainage into deeper levels (recharge). The soil moisture profiles at depth are evaluated using geophysical techniques that allow for the tracking of recharge fronts. After rainfall events, the distribution of its fate between runoff, evaporation and recharge is determined. Water in the soil beyond the field capacity can be demonstrated to mostly contribute to the ultimate groundwater recharge in the area. Water stored beyond the permanent wilting point is not considered to contribute significantly to the recharge regime. Because of the irregular nature of rainfall, the amount of recharge is found to be related to the spacing of wet and dry spells during the winter months more than the actual amount of rainfall. Prolonged dry periods allow for excess water to drain into the deeper soil and thus to the groundwater, and thus allow for more uptake following subsequent rainy events. Evaporation does not significantly contribute to the drying of the soils. Reanalysis of rainfall and evaporation data from previous years suggests that recharge rates range from 20 to 37 % of total rainfall amounts, as opposed to the currently assumed 5 %.