ORIGINAL PAPER Seasonal variations in water quality of Al-Wehda Dam north of Jordan and water suitability for irrigation in summer Ahmed A. Al-Taani Received: 1 June 2011 /Accepted: 27 September 2011 /Published online: 14 October 2011 # Saudi Society for Geosciences 2011 Abstract Al-Wehda dam is an impoundment on the Yarmouk River basin north of Jordan, which came recently into operation. The reservoir is designated to provide water for agricultural, domestic, and industrial uses. Evaluation of seasonal trends in water quality of Al-Wehda dam over the year 2010 showed strong influences by weathering and leaching of geologic units along with discharge of effluents from the adjacent agricultural lands. Seasonal trends in TDS level showed slight variations, though its concen- trations have been affected by events of rainfall and evaporation. The presence of total nitrogen (TN) and total phosphorus (TP) promoted the development of photosyn- thetic algae. Temporal fluctuations in TN, TP, chlorophyll a, COD, and BOD have been observed with peaks occurred in spring season. TN to TP ratios varied seasonally with a minimum ratio observed in spring concurrent with algal bloom. Eutrophication tends to occur throughout the year, though its intensity increased in springtime. A variety of water quality parameters has been used to evaluate water for irrigation use during summer time when the water demand for irrigation increased. Of all parameters evaluated, Na% and TH indicated that the reservoir water is not suitable for irrigation purposes. Keywords Al-Wehda dam . Seasonal water quality . Algal bloom . Irrigation water . Jordan Introduction The demand for water has been growing rapidly in Jordan in response to increasing population growth and rapid agricultural and industrial developments. While there are very limited water resources in the country, the water scarcity problem has been recently exacerbated by persis- tent drought. The increased demand for water has been partly met by excessive withdrawal of groundwater beyond the safe yields. In addition to reducing the exploitable quantities, over-extraction of groundwater resources has degraded water quality. In Jordan, agriculture is the major consumer of water resources and expansion in irrigated agriculture has been rapid in recent years. In 2000, the agricultural sector consumed around 66% of water resources, although it contributed less than 4% to the gross domestic product (Nortcliff et al. 2008). The municipal sector is the second largest consumer of water with about 30% of the annual water consumption. In addition to water quality issues, securing further water resources to meet future needs remains of central impor- tance in Jordan. A great deal of efforts have centered around the construction of dams. Al-Wehda dam is an example of a long-term solution to water scarcity in north Jordan which the government has invested on. It is an impoundment on the Yarmouk River basin which is designated to provide storage for agricultural, domestic, and industrial uses. While significant portion of basin catchment is located in Syria, lack of bilateral cooperation renders it difficult to control water quality feeding the dam. Of equal importance is the reduction in the quantities of water in the reservoir because of diversion of Yarmouk A. A. Al-Taani (*) Department of Earth and Environmental Sciences, Yarmouk University, Irbid 21163, Jordan e-mail: taaniun@hotmail.com Arab J Geosci (2013) 6:1131–1140 DOI 10.1007/s12517-011-0428-y