Samples of water and sediments were collected from three sites along the main body of King Talal Dam (KTD) in the period
between Spring 2007 and Winter 2008. The sites represent the middle point of KTD (site A), its deepest area (site B) and its
outlet or intake point (site C). Samples were collected from surface and near-bottom water during four seasons within the
study period, while the sediment samples were collected during dry (summer) and wet (winter) seasons within the same study
period. In addition to temperature, dissolved oxygen (DO) and pH, water samples were analyzed for nitrate (NO3-), nitrite(NO2-), ammonia (NH3), dissolved inorganic phosphate-phosphorus; DIP (PO4-), total nitrogen (TN), and total phosphorus(TP) contents. Sediments samples were analyzed for grain size distribution, organic matter, total phosphorus (TP), and total nitrogen (TN). Nutrients in water fluctuated in space, depth and time. Nitrogen species concentrations were highest during spring, while higher phosphorus species concentrations were recorded during winter. However, nutrients showed significant differences between seasons and insignificant differences between sites and between depths. The concentrations of nutrients in the water were generally less than their concentrations in the sediments. Nutrients in sediments showed more or less
similar general trend of spatial distribution, where maximum values occurred in site A and site B during winter, and most of
the pollutants decreased towards the far end of the dam at its outlet or intake point (site C). The concentrations of nutrients
were higher in the clay–silt size fraction (<63μm), which has higher organic matter contents compared to the larger size
fractions. The results of the present study agree with and confirm the results of many previous studies which indicated that
water and sediments of KTD are polluted due to many anthropogenic and natural sources. The results and its relationships
with these sources are discussed in details.