The optimal management of regional aquifers subjected to intensive withdrawal for irrigation
has been attempted for al Busayata, Wadi Al – Sirhan, in Al-Joul, Northern Kingdom of Saudi
Arabia. The objective is to control the groundwater level behavior when optimal amount of
water required for agriculture activity is abstracted from the aquifer, Al-Busayata area has
been selected as a key area for detail investigation of water resources. The aquifers in the area
are non-homogenous in behavior. Two tires aquifer system had been considered with different
hydrologic properties. The regional stratigraphic and structural geological framework of the
area, landform characteristics, metrological parameters and hydro geological milieu has been
used for aquifer simulation. The geometry of Al Jouf and Tabuk aquifers were obtained from
the drilling and geophysical logs, and wells design data obtained from records. The 3-D
simulation was carried out assuming saturated, two tier aquifer, three slices, verticval
Exaggeration 1:1, horizontally disposed aquifer, confined, steady state flow, constant time
steps, six node triangular prism, 21776 mesh elements, 14250 mesh nodes, constant head
boundary in the north and north east, no-flow boundaries in the eastern and western extremes
of the study area, southern boundary is considered to be constant recharge boundary. The
Water levels were simulated using well discharge data obtained from irrigation projects in the
study area with optimization routine runs, iteratively. The transimissivity and storativity as
constant and changing the q (draw down). Keeping all other assumptions same only selective
pumping was attempted.
The initial heads of 1987 were used and were calibrated using 1991 heads. Five wells namely
W12, W43, W70, W81 and W83 were pumped for 20 years, since in these parts the drawdown
is minimum. Four trail runs were carried out to arrive at good agreement between observed
and calculated values. Consideration of the present water levels and abstraction rates and the
resulting heads on comparison with the initial heads show lowering of water level in the area.
The calibrated model has been used for predicting water level of aquifer as influenced by
irrigation water requirements of alfalfa, wheat, tomatoes and potatoes for the year 2001. The
groundwater level was controlled by selective pumping and managed by simulation. The
cropped area for alfalfa, potato, wheat and tomato has been calculated using Landsat TM FCC
432. Using the Penman-Monteith method, the average daily requirement for alfalfa is 94m3/-
day/ha, potato is 54.0633m3/day/ha, wheat is 53.94 m3/day/ha and tomato is 69.13 m3/day/ha.
Dr. Yousef A. Al-Rumikhani
http://www.wsta-gcc.org/includes/New%20Folder/HTML/ke12.htm 2
The seasonal water requirements for alfalfa, potatoes, wheat and tomatoes were 2700 million
m3, 34 million m3, 27.14 million m3, and 26.086 million m3 respectively.
The withdrawal of 2787.226 million m3 water from the aquifers resulted in water level drop of
5 to 20 centimeters.The groundwater level van be managed using irrigation scheduling and
avoiding over irrigation in the irrigated schemes.
It is recommended that the daily crop water requirement for each crop should be calculated for
each growth stage and the irrigation schedule shall be prepared to avoid over irrigation and
minimize the use of precious water resource. The groundwater level can be managed using
irrigation scheduling and avoiding over irrigation in the irrigation schemes