M. Hachicha et al., The impact of long-term irrigation on changes of ground water level and soil salinity in northern Tunisia, ARID SOIL R, 14(2), 2000, pp. 175-182
The irrigated area of Kalaat Landelous in northern Tunisia is an example of
the successful reclamation of 3000 ha of soils affected by shallow ground
water levels and salinization. Examination of soil conditions at three key
periods during reclamation reveals the reasons for this success. Aspects of
irrigation management define these periods, during which measurements were
taken of the depth and salinity of ground water over 43 years. An overall
salt balance for the irrigated areas was made in order to estimate the risk
of salinization. The results reveal a lowering of the ground water level (
average depth was I m and will be 1.6 m), desalinization of the soils (aver
age electrolytic conductivity of the soil was 0.8 S m(-1) and will be 0.55
S m(-1)), and dilution of the salt content of the ground water (average ele
ctrolytic conductivity of ground water was 3 S m(-1) and will be 1.4 S m(-1
)). A reduction in the variability of saline conditions was also observed.
The salt balance shows a large amount of salt exported from the area, betwe
en 22,000 and 66,000 Mg, and only small areas of new salinization have appe
ared as a result of irrigation. Ultimately, the sustainability of the proje
ct depends upon the performance of the drainage network and on the abundanc
e of the rainfall. If drainage is efficient, soil salinity will be maintain
ed below wheat, corn, tomato, pepper, and alfalfa tolerance limits.