Diurnal Periodicity in Ground Water Recharge Rates

by Stephen N. Webb, Engr.; School of Civ. Engrg., The Univ. of New South Wales, Sydney, Australia,
Keith K. Watson, Assoc. Prof.; School of Civ. Engrg., The Univ. of New South Wales, Sydney, Australia,

Serial Information: Journal of the Irrigation and Drainage Division, 1978, Vol. 104, Issue 1, Pg. 69-77

Document Type: Journal Paper


In an investigation of the flow characteristics of a recharge pit used for artificial ground-water recharge purposes, diurnal variations of a cyclic nature were detected in the intake rate. The output from soil water pressure sensors installed between the base of the pit and the water table indicated similar cyclic variations. The maximum intake rate occurred regularly each day at approximately 2 a.m. - 3 a.m. and the minimum approximately 12 hr later. It is concluded that these variations are due to the activity of algae on the base of the pit and in the top layer of sand. Diurnal peaks and troughs of the algae oxygen production result in changes in the hydraulic conductivity of the profile. This would appear to be related to changes in the volume of the occluded oxygen which exists as bubbles in the soil pores. These reduce the flow area available for recharge and thus cause a reduction in the intake rate.

Subject Headings: Water pressure | Groundwater recharge | Groundwater flow | Water intakes | Soil water | Soil pressure | Water table | Vegetation

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