Monitoring the Change of Water Level and Its Effect on Water Quality in Sawa Lake, Southwest Iraq

Abstract

Sawa Lake is considered one of the distinct closed water systems located in the southwestern part of Iraq. In last years, the lake has suffered from a significant decrease in the water depth reached 1.5 m, thus the current study aims to monitor and analyse the change in water level, and identify causes and effect of this change on the lake hydrochemical properties by using analyzing cations and anions with the assistance of sub bottom profilers technique as well as obtained information from scientific diving.
 The results revealed that the lake had an equilibrium state between feed up and withdrawal water as well as evaporation during history. In spite of the high evaporation rates in the region, this equilibrium state made the lake doesn't dry up completely or become as a high salinity water system as brine lakes or as the Dead sea system. The equilibrium state is due to recycling and washing process of salt water by filtration and leakage under the bottom of the lake through the recharge site, so, there is a replacement of water, the decreasing in the lake level is not only attributed to evaporation factor, the main reason for this decreasing resulted in reducing the supply of Dammam aquifer, which is considered the main water supply effecting of the lake.

The Water Area of Sawa Lake as Derived from Land Surface Temperature and Remote Sensing Data

“…The topography of the study area increases at a rate of 2.7 m per km as we move from the northeast to the southwest [2]. Sawa Lake has an area of 4.7 km2, a maximum length of (13.5 km), a maximum width of 1.936 km, and a minimum width of (0.5 km) [10]. A gypsum barrier surrounds it, its height ranges between (2-5)m, and its length is (12.5 km), which makes it isolated and closed to the surrounding area [4].…”

“…This was obtained during (2020-2021) from the meteorological data of the study site for NASA. The surface temperature of the study area was measured from the band (10) by converting the reflected spectral radiation from the region to the brightness temperature, which was done using the data from the heat band file (10). The following brightness temperature equation was applied [31]:…”

“…Because of the intense evaporation, the lake was exposed to many current studies investigated its impact on the lake and showed that the depth of the lake water decreases over time. The lake water depth was about 4 to 5 m 35 years ago, and the water depth has become between 1-2 m in recent years with the continuation of the decrease in the vicinity of the lake along with the reduction of its surroundings [10]. As a result of the lake being located in a desert area characterized by drought and high temperatures in the summer and the increased demand for water resources to meet agricultural land needs, all of this affected a decrease in groundwater levels [11].…”

Monthly drought monitoring of the surface water area of Sawa Lake, Iraq during 2016-2022 using remote sensing data

“…Consequently, it is assumed that the lake has a remarkable water recycling (washing) system, which may represent the second reason for the decrease in water and evaporation. [30]. All of these components contribute to the Sawa lake features to meet all four natural criteria for outstanding global qualities needed for inclusion in the World Natural Heritage List [28].…”