In approaching the task of developing recharge estimates for dam sites, several constraints are apparent, including the scarcity of site-specific data for the selected new sites and the availability of simple yet robust analysis techniques. Combined, these constraints require an approach which involves best use of available data, adoption of relatively simple analytical approximations of reality, and the adoption of several key assumptions. In arid country with limited resources, two simple techniques have been used for recharge estimation: (1) a simple water balance model in spreadsheet and (2) a more refined Darcian approach involving an analytical approximation of a flow-net solution. By applying the two models at three new dam sites, the amount of recharge rates calculated over the period 2007-2026 was close. This is because, despite Darcian approach that should have affected the recharge rate as other parameters were introduced in the calculation of q t , e.g., groundwater table mound, reservoir water height, etc., the results show general agreement between the two methods which seem to validate the assumptions made in both methods. A general conclusion of this comparison is that the hydraulic conductivity (K) is the main determining factor in recharge calculations in these situations. The water balance model was used to estimate recharge at Wadi Bahaman, under gravity and cascade dams' scenarios. Using gravity dam at Wadi Bahaman for groundwater recharge proved not suitable based on the relatively small predicted runoff from a small catchment area and geological concerns in the abutment areas. Instead, a series of three low check dams(2 to 4 m high) was proposed. These check dams will slow down the runoff flow, form small reservoirs, and enhance recharge along the valley, without requiring expensive foundations. Estimated groundwater recharge under cascade dams (141,407 m 3 /year) is greater than recharge estimated for gravity dam (103,853 m 3 /year) by at least 36%.
Credible estimates of recharge are essential for assessment of sustainable water resources in semi-arid areas, which rely on groundwater for irrigation and domestic supply. Investigation of the mechanisms and rates of recharge to the aquifers of the Sana’a Basin, Yemen, showed that the main components of recharge are infiltration of surface flows, irrigation return and urban leakage. Limited data and inaccessible, mountainous terrain required the use of robust, low-cost methods of quantifying the recharge components. Infiltration of surface flows from 12 wadis averages 39 Mm
3
a
−1
, with high interannual variation. The recharge was calculated using a combination of a rainfall-run-off model and computation of the water balance for the wadi. Irrigation return flows of 30 Mm
3
a
−1
, 20 to 40% of the water applied, were derived from measurements of soil moisture and matric potential for the three most extensive crops. Urban recharge from mains leakage and seepage through septic tanks was estimated from a well inventory, water supply records and usage rates, as 59% of the water supplied. The total recharge to the aquifers of the Sana’a Basin in 1993 was estimated to be 102 Mm
3
, significantly less than the total groundwater abstraction, of about 184 Mm
3
.
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