Applying geographic information systems (GIS) techniques to estimate surface area of Al-Razzaza Lake, Karbala province, Iraq

Countries with dry and semi-arid climates, like Iraq, employ manmade or natural water bodies to regulate river levels and store water during flood seasons, preserving the ecosystem’s equilibrium. The goal of the current study was to determine the surface area of Lake Al-Razzaza, which is situated in the Karbala Governorate of Iraq, using an integrated approach based on geographic information systems and remote sensing. Landsat satellite images taken in October 2015, 2019 and 2023 were used as a source of data to monitor the changing area covered by the lake. The results showed that the surface area of the Al-Razzaza Lake was 363 km2, 316 km2, and 221 km2 for the years 2015, 2019, and 2023, respectively. It was observed that there was a slight difference in the surface water area of Al-Razzaza Lake between 2015 and 2023, estimated at 47 km2, while there was a decrease in the area of the lake in 2019, estimated at 142 km2. This study demonstrated the effectiveness of GIS technology and Landsat satellite images in topographical analysis of water bodies and monitoring water bodies over large areas in a short time and at a low cost.


Introduction
The issue of water in Iraq, which has an arid and semi-arid climate, is one of the most important aspects of maintaining ecosystems to ensure that people have the food they need.The main source of irrigation, drinking water, and energy production in Iraq is the Tigris and Euphrates rivers.In addition, there are a number of natural and artificial water reservoirs, spread out in many areas of Iraq, that draw water from river water for storage during flood seasons.These bodies of water, whether natural or artificial, are considered one of the most important elements in maintaining balance and are used, whether natural or artificial, primarily to maintain rivers at the appropriate water level and to store river water during flood seasons for later use when the rivers are low.Studies related to lake water are important, because it is one of the water supplies for domestic use, industrial uses, and crop irrigation, as well as to support life, whether for humans, plants, or animals [1].Attention to water quality is essential and no less important than its quantity [2].One of the biggest concerns facing the region in general is climate change [3].Al-Razzaza Lake, which was chosen in this study, is one of the large low-lying lakes located on an area of 1810 square kilometers [4].The main objective of the current study is to use GIS technology and data from remote sensing to estimate surface changes in the water area of Al-Razzaza Lake.As shown in Table 1, several current studies on the management of water resources for Al-Razzaza Lake use a combined approach of computerized geographic information systems and remote sensing.

Technique and data used Author
The total area of the marshes increased by 85% in 2012 while the total area of selected lakes decreased by 15 [5] The rapid decrease in the lake area by 81.17%.usingNDWIs and with a percentage of 79.69% using NDVIs and an area of about 1187.40 km 2 and 1189.24km 2 , respectively.

Landsat satellite images Hayder
Dibs, 2018 [6] The storage capacity of the Dokan Dam reservoir decreased by 28% due to sedimentation, which is estimated at 7 million cubic meters annually.
A bathymetric survey A single-beam echo sounder ArcGIS software Topographic maps Rebwar et al., 2019 [7] The Al-Razzaza Lake's level of water varied according to the season.Between 2000 and 2015, the lake's area and height fell by about 320 km³.
Landsat TM, ETM+.Arc GIS 9.3 ERDAS 14 Microsoft Excel 2010 Sabah et al, 2021 [8] There is a particularly sharp change in the water levels of Lake Razzaza and there are large fluctuations in the lake level and water surface area over time.

Landsat. TM, ETM+ and OLI for 1990, 2000 and of 2016
Al-Qaraghuli et al. 2021 [9] According to the findings, there was a 63.4 percent decrease in the Al-Razzaza Lake shoreline between 1989 and 2019.
Landsat satellite images and with the help of GIS Huda et al., 2022 [10] The Mosul Dam Lake's maximum area was 320 km2 in 2005, while its minimum water surface area was approximately 225 km2 in 2010.
IOP Publishing doi:10.1088/1755-1315/1300/1/0120083 ` Al-Razzaza Lake was a large and deep lake, but over the past ten years the water level decreased significantly, reaching only 5-10 meters in depth, and the salinity increased due to the loss of recharge from Al-Habbaniya Lake [13].Climate changes also led to a decrease in the lake level due to increased evaporation during extremely dry and hot summers, also the discharge of wastewater into the city of Karbala contributed to the decrease in the lake level [13].

Geological setting of Al-Razzaza Lake
The geological environment of the study area is characterized by an age range extending from the Upper Miocene to the Pliocene [14].The Ingana Formations (U.Miocene), Beard (Pliocene-Pleistocene) and Quaternary sediments (Pleistocene-Holocene) represent the main formations that constitute the stratigraphic succession in the two study areas (Table 1).Table 2. Description of the lithological formations in the study area [15] Tectonically, the Iraqi land platform is divided into two basic units: stable shelf and unstable shelf [15].A stable shelf is characterized by a low thickness of sedimentary cover and little folding, while an unstable shelf is characterized by a thick and folded sedimentary cover.The folds are arranged in long narrow convex lines and broad flat synclines [15].The study area is located in the stable cliff (Al-Rutba area -Al-Jazeera), where there are many faults, the largest and most important of which is the Euphrates fault, which extends from Hit to the northwest of Samawah city.

Methodology
The method used in the current study is the integration of remote sensing technology and geographic information system (GIS) to conduct an unsupervised classification for the purpose of extracting the borders

Satellite image processing
A georeferenced LANDSAT 8 satellite for the years 2015, 2019, and 2023 were downloaded from the free USGS website.It has two sensor: operational land imager (OLI) and thermal infrared sensor (TIRS).OLI sensor has 9 bands with 30m spatial resolution (except for panchromatic band) and the TIR sensor has two thermal bands with 100m spatial resolution.Landsat images undergo processing to carry out various operations aimed at enhancing their quality or extracting valuable information.The common image processing functions available in image analysis systems can be classified into layer stack, mosaics and subset as shown in Figure 3.
In order to improve the accuracy of the downloaded Landsat image of Al-Razzaza Lake the eighth band, with a resolution of 15 m, was merged on the merged bands by merging the resolution, and thus it was possible to obtain an image of the area with a more appropriate resolution.
A mosaic was not created for Al-Razzaza Lake, because one satellite image covers the lake area, so there is no need to create a mosaic for all periods studied (2015, 2019 and 2023).Extracting the region of interest from the images/mosaic is a sub-preparation of the study area.By removing unnecessary data from the file, this technology speeds up the processing process because there is less data to process.Larger image subsetting to reduce file size, and thus the computing overhead of image processing, can be more effective when image coverage exceeds the study area.Al-Razzaza Lake subset for the years 2015, 2019, and 2023 are shown in Figure 4, 5, and 6 respectively.Al-Razzaza Lake `

Lake Mask extraction
To isolate the water layers from other categories requires a classification, which entails the process of assigning spectral categories to information categories, in order to identify the changes that occurred on the coast of Al-Razzaza Lake between 2015 and 2023.The two most common methods of classification are supervised and unsupervised classification.In this study, an unsupervised classification was performed for the purpose of clarifying water boundaries (lake mask extract).The results showed that the study areas were divided into three different categories based on spectral reflectance values from satellite images The resulting thematic maps of an unsupervised classification for the periods of 2015, 2019 and 2023 are shown in Figures 7, 8 and 9, respectively.However, for the purpose of determining the exact boundaries of the lake, the image was reclassified using Arc GIS software into only two categories, aquatic and non-aquatic using the Normalized Difference Water Index (NDWI).
It is the difference in light absorption and reflection between water and other features in different frequency bands allows surface water areas to be mapped using multispectral remote sensing images.Normal difference water index (NWDI) is one method of spectral enhancement which is a nonlinear mathematical transformation used to highlight areas covered by water.The spectral reflectance of water is high in the green wavelength region and relatively low in the near infrared wavelength range, which is the basis of this index.Because of the soil's and vegetation's high infrared reflection, water regions have positive NDWI readings.The reflectivity of vegetation, aquatic bodies, and arid regions is displayed in Figure (10) based on the wavelength.

Estimation of surface area of lake
It has been noted that traditional study methods for detecting changes in water levels over large areas are expensive and take a long time, so remote sensing techniques and geographic information systems (GIS) were used in this study to monitor changes in the water of Lake for the year of 2015, 2019, and 2023.Through the use of satellite images taken at different times, the area of change covered by the lake was monitor (Figure 14).
When comparing the field measurements for the lake level made by the Ministry of Water Resources for the three periods, it was found that the lake level was slightly lower in 2019 than from 2015 and 2023, as shown in Figure 15.
The lake area in square kilometers was calculated for the three periods using GIS software.The calculation method depends on the spatial resolution of the Landsat satellite image, which is 30 metres, meaning that the area of one pixel is 900 m 2 .All pixels that fall within the lake shoreline are counted, while any pixels more than half outside the lake shoreline are not counted.
The area field was added to the attribute table in the GIS program, where the area in square kilometers was calculated for each pixel located within the shoreline of the water body, and then the area of the lake was calculated by calculating the areas of all pixels within the boundaries of the lake.It turns out that there was a slight difference in the surface area of the lake between 2015 and 2023, estimated at 47 km 2 , although the average lake level was 0.07 m between the two years.However the surface water area of the lake was less in 2019 compared to 2015 and 2023, a difference of 142 km 2 as is clear in Figures 15 and 16

Conclusion
Remote sensing and GIS techniques were used to identify and analyze changes in the area of Al-Razzaza Lake.The calculated surface area of the lake water after knowing its levels and extracting its boundaries for the three periods was about 363 km 2 , 221 km 2 , and 316 km 2 for the years of 2015, 2019, and 2023, respectively at different elevation water levels.According to the findings, Al-Razzaza Lake's surface water area as determined by satellite photos was at its lowest in 2019, differing by 142 km 2 from 2015 and 47 km 2 from 2023.

Fig. 4 :Fig. 3 :
Fig. 4: Sub setting of the study area for the year of (2015)

Table 1 :
Studies used GIS and remote sensing techniques in monitoring changes in water bodies in Iraq .5% in 2012.