Ancient and Recent Challenges in the Utilization of Soil and Water Resources in Egypt.
Salah A. Tahoun, Soil Science Dept, Univ of El-Zagazig, El-Faluga Street, El-Zagazig, Egypt
Pre-history Egyptians were nomadic pastoralists living in sub-humid rangeland across the eastern and western plateaus away form the wild River Nile of the time. At the end of the Holocene, the ecosystem was disrupted by intense climatic changes which initiated everlasting hyper-aridity testified by the present Eastern and Western Deserts as parts of Sahara. Starvation forced people to escape ca 8000 years BP to the wild Nile Valley. Some clever settlers noticed that the Nile floods come with certain periodicity over time, and thus invented the first human calendar. Shortly afterwards, settlers improvised basin irrigation where fences of earthy materials were piled at distances from the river to elevate the water front and bring land under a water head of about 2 meters for about 2 months. Fences were removed as flood began to recede to flush water towards the shrinking river. In normal-sized floods, sufficient water was stored in soils to meet the requirement of subsequently cultivated crops. As food surpluses were produced, individuals were differentiated for societal division of labor, a pre-requisite condition for civilization to emerge. About 6000 years ago, a genius Egyptian “agricultural engineer” hitched an ox to a hoe and invented the plow, thus initiating power farming for the first time in history. Basin irrigation endured for millennia because of its simplicity, efficiency, and cost-effectiveness. Actually, the Nile River performed simultaneously three functions. It provided needed irrigation water, disposed of virtual drainage water, and rejuvenated soil fertility with nutrient-bearing minerals adventitiously added during inundation. Communities of the Greco-Roman time some 2300 years BP learned to erect earthy dikes across distant segments of the Nile during the low-water season. Elevated river front allowed water delivery to highly situated land. Several “irrigation machineries” most important of which is the water wheel were also developed, and therefore, more land was brought under cultivation. The mid-nineteenth century witnessed significant evolution of irrigation engineering in Egypt. A series of barrages were constructed and many canals were dug. However, the system worked well only with medium floods. Many catastrophic years were encountered with meager floods smaller than 40 cubic kilometers of water or overwhelming floods larger than 120 cubic kilometers. To cope with these extreme events, the Aswan High Dam was constructed in the sixties of the twentieth century to establish a decadal reservoir saving water from lavish to lean years in the huge Lake Nasser, extending 500 km upstream. Water from the lake is carried northward to irrigate 5.8 million ha of intensively cultivated land through an intricate network of canals that extend for 36,000 km. Basin irrigation is now an antiquity replaced by calibrated methods that raise the irrigation efficiency in places to 75 %. Paired with international statistics, the soils of Egypt stand very productive in terms of yield tonnages per unit land area. Looking in retrospect, ancient Egyptians are commemorated for their many contributions, including the primitive earthy fences intended to elevate water front that developed after millennia into the Aswan High Dam. The common bottom line is enhancing agricultural production and minimizing the energy requirement of the irrigation system. Notwithstanding these achievements, recent socio-economic and demographic variables in Egypt are confronting the agricultural sector with intrinsic and sectoral challenges. First, intensive soil utilization is raising concerns of potential soil degradation and environmental pollution. Second, the growing industrial, service, and civic sectors are crying for an equitable water share, and their demand is augmented by calculations based on the water productivity concept. These challenges could be met by a program of four-fold objectives: adopt an appropriate land use policy, convey and deliver irrigation water more efficiently, produce sustainable higher yields per unit water, and maintain environmental integrity.