Recent urban development tremendously increased the use of water in domestic, industrial and landscape irrigation which increased manifold production of wastewater of marginal quality. Saudi Arabia is an arid country having limited and non-renewable groundwater resources coupled with un-predictable and scanty rainfall. The growing demand of good quality water for various purposes has forced the water planners to find an alternate sources of water to lower burden on freshwater groundwater resources. In Riyadh city, about one million cubic meter of wastewater is flowing daily in Wadi Hanifah. To explore the quality of that water and its effect, a study was carried out along the main drainage channel known as "Wadi Hanifah Stream" often called as man–made-river to examine its quality including chemical composition, its predictive effects on soils and management alternatives for re-use for landscape irrigation in and around Riyadh city. The wastewater channel is composed of agricultural drainage water, sewage water, seepage losses from irrigated fields, leakage from water supply systems, runoff from over irrigation and waste effluent from Wastewater Treatment Plant Riyadh. Water samples from 31 locations along Wadi Hanifah stream were collected for quality evaluation for its reuse in landscape irrigation.
The SAR and adj.RNa of wastewater ranged from 4.06-7.66 and 4.75-10.75, respectively. The B concentration was above the permissible limit of 1.0 mg L-1 for crop irrigation. The predicted soil salinity values from hypothetical leaching fractions showed that the soil salinity falls in the category of moderate to highly saline soils where cultivation of moderate
to high salt tolerant crops is possible provided 15-20 % excess water above crop water requirements is applied as leaching requirement to maintain soil salinity within acceptable limits. Careful analysis, improved irrigation systems and irrigation management practices are key factors for reusing drainage water.