GROUNDWATER CONTROL OPTIONS AT IMPORTANT ARCHAEOLOGICAL SITES IN THE NILE VALLEY, EGYPT

Damage to ancient monuments, buildings, and tombs is widespread particularly in the irrigated areas of the Nile Valley. Evapotranspiration continues to increase salinity of shallow groundwater and surface water adjacent to many antiquities. A rising and permanently high water table in the irrigated areas of the Nile Valley is accelerating damage to ancient monuments, buildings, and tombs. The absence of any vapor barrier in the foundations allows capillary water uptake in the stone and mud-brick walls, with subsequent deposition of salts within and on the surfaces of evaporation. Changes in hydroscopic moisture content vary with relative humidity and contribute to surface deterioration following salt emplacement. Microbiological activity is expected to flourish within niches where moisture and water quality permit. Art and building damage is manifest as staining and discoloration of the surface and loss of paint, as well as granulation and spalling of the stone. Capillary water must be controlled to prevent further damage.

Passive groundwater control measures are preferred over the more costly active systems that require pumping equipment and regular maintenance. Capillary barriers can be constructed at antiquity sites to protect foundations, particularly from the shallow water table in irrigated areas. Passive systems include physical dams, canal linings, sheet piles, grout curtain and clay cut-off walls. Hydraulic sinks include drainage trenches, tiles, connector wells and flowing artesian wells. Active systems are more process oriented and may include pumping wells, trench sumps, and sand point de-watering systems. The high and sustained costs for power and maintenance discourage the use and deployment of active systems, unless they are integrated with other practices such as sewerage control and groundwater development projects. Where active and passive systems must be combined, operational costs may be reduced by using, solar and/or wind power. Selection and design of cost-effective water control measures require an adequate hydrogeologic site characterization effort, as illustrated by recent studies on the Hierakonpolis site in southern Egypt. Removal of existing salt and microbiological control demand innovative approaches to overcome a formidable challenge.