Hydrology and Water Quality

Bosherston Lakes in west Wales are an internationally important set of linked freshwater lowland lakes which were created by damming tidal creeks in the 18th and 19th centuries. The lakes have an average water depth of 1–3 m, and receive surface water inflows but have an uncertain interaction with the underlying karstic Carboniferous Limestone. This paper describes the application of the Soil Water Assessment Tool (SWAT) to improve the understanding of the hydrological functioning of the lake system. The temporally variable and limited observational data were used within a two-step calibration process. The simulated surface water inflows and groundwater levels were calibrated, followed by the lake volumes (Nash–Sutcliffe (NS) coefficient ranging from 0.67 to 0.74). Finally the simulated lake volumes were validated (NS ranging from 0.56 to 0.74) and the simulated lake outflows demonstrated to be plausible. Simulations reveal that three of the four linked water bodies lose significant water to the underlying aquifer. The simulated water balance demonstrates that the catchment outputs are dominated by evapotranspiration, surface outflow from the lake system to the sea and coastal groundwater discharge, with abstraction and lake evaporation being of lesser importance. The coastal groundwater discharge originates from both leakage from the lakes and previously unrecognised larger scale groundwater flow paths in the limestone aquifer. The study has provided an improved basis for the future hydrological management of the catchment and lakes and has demonstrated the wider utility of SWAT in simulating karstic systems.

Hydrological changes in the lower part
of  Mesopotamian Basin
Hassan K. H. AL-Mahmood
Marine Sedimentlogy  Department. Marine Science centre,
University of Basra- Basra- Iraq
[email protected]
Abstract
  This study was examined the hydrological changes in the water-ways for the River and the marshes associated with them in Southern part of lower Mesopotamian catchment area (Tigris and Euphrates Rivers and their branches in Amarah, Nasiriyah and Basra ) and the main tributaries of the Shatt al-Arab River( Swaib, Garmat Ali and Karun ), and the significant changes in the overall hydrological conditions of water discharge and water quality. Water discharge and water samples were collected quarterly for four sites during 2011, the laboratory analysis were performed to determine physical and chemical characteristics at these sites.
  Results shows that the quarterly water discharge seasonal rate in Tigris River  is 41.05 m3/s at Qalaat saleh, Euphrates River at Chabaish 11.65 m3/s, Shatt Al-Arab River in Qurna 39.65m3/sec, that the Garmat Ali to cause the loss of an average of 20.1 m 3 / sec from Shatt al-Arab water into to Hor Alhammar, during a seasonal fluctuation between summer and winter, causes water relapsing during the winter  water Contamination  of the central part of the Shatt al-Arab.  Clear water shortage reflected on water quality in Southern Iraqi Rivers and their branches. While water salinity is ranging between 1.31-1.42 gm/l in Tigris River, 3.46-5.15 gm/l in Euphrates River, 2.00-2.29 gm/l in Garmat Ali River, 1.00 -1.98 gm/l in Ezz River and 1.59-1.83 gm/l in Shatt al-Arab River
  This study shows that the Tigris and Euphrates Rivers suffer of large water scarcity and lack of supply from Swaib and Garmat Ali Rivers to the Shatt al-Arab, as well as  stop the flow of Karun River to the Shatt al-Arab and wasting a large portion of water from the Tigris and Euphrates Rivers to restore some parts of Southern Iraqi marshes. the contribution of the Euphrates River in the salinity of the Shatt al-Arab 50% during  the winter, Although the total discharge does not exceed 25% , and the contribution of  the Garmat Ali  30% and 20% of the Tigris River, while the effect of the salt of the Tigris River 100 % during the summer. The study concludes that the hydrological situation in the study area is  continuous  deterioration due to absence of any instant or far-reaching strategies to handle this deterioration, which calls for the intensification of future studies in various disciplines related to water resources management.

Keywords :  lower Mesopotamia - Tigris and the Euphrates River - hydrological Rivers  in south of Iraq - the Shatt al- Arab River  - fresh waters  of Iraq