Using GPS and Run-Off Rates Data to Study the Close Monitoring Networks for Dams – Al-Kut Barrages as a Case Study

The dams and barrages are among the most important engineering structures for water supply, flood control, agri - culture, and electric power generation. Monitoring the horizontal and vertical deformation of the barrage’s body and identifying the risk it’s so important to maintain the dam and also to reduce costs. Where in this research the case of the Al-Kut barrage is studied by observing the body of the barrage using surveying devices through (GPS) by taking spatial observations of the two networks of stations, the horizontal and vertical networks. Then compare them with the observations of previous years to determine the magnitude of the deformation through the differ - ences between the observations. By calculating the differences and finding the displacement of surveying observa - tions from 2014 to 2021, It was found that the highest and least displacements in the horizontal stations is 50 and 11 mm, respectively. Also, for the vertical network observations, the highest and lowest differences in elevation were 11and 3 mm, respectively. Where, the results showed a slight deformation within the acceptable limits. In addition, the annual and monthly discharge rates for a number of years were evaluated to observe the extent of the impact of run-off rates on increasing sedimentation at the upstream of Al-Kut barrage. It was found that the accumulation of sediment on the river’s left bank affected the gates’ efficiency and put pressure on the other gates, which led to some operational issues in the barrage gates.


INTRODUCTION
Monitoring deformations for important engineering facilities is one of the most important applications of geodetic engineering works, which accompany the construction phase and continue during the investment phase, which aims to assess their conditions and safety as well. Determining the displacements of a facility during a certain period based on periodic measurements of the networks of the horizontal and vertical stations. Monitoring stations consist of control points and reference points, where periodic surveying measurements are carried out and the results of the measurements are processed to obtain accurate results. In addition, the presence of multiple vertical and horizontal reference stations for the monitoring network is necessary to improve the accuracy of these surveying measurements. In addition to ensuring the stability of the reference stations from time to time. The stability of the network stations is studied by comparing the results of the differences for the measured elements .
By knowing the difference between previous and recent observations, the impact of the barrage infrastructure over time is known. The main objective of studying the difference between the observations is to detect unexpected horizontal and vertical deformations at an early stage, and thus assess the infrastructure and integrity of the barrage. Where the results of measurements of deformations is important for engineering installations and constitute the basis for evaluating the safety  [Bayik et al., 2021;Goff et al., 2021], thus addressing the deformations at an early time, before it is too late. The cracks and movements in the elements of the facility may lead to its exit from service or may lead to its collapse, causing major disasters and human disasters, especially in dams and barrages [Goff et al., 2021].
Therefore, the use of modern technologies such as surveying devices associated with the global positioning system (GPS) is one of the most important modern methods and systems in monitoring and evaluating the barrages. Thus identifying potential risks and maintenance requirements to avoid disasters, as well as with the help of GIS programs in the study, analysis, collection of results, and the creation of maps and graphs ( Figure 1) [Li et al., 2020].
Al-Kut Barrage is located in Wasit Governorate in the city of Al-Kut on the Tigris River. The barrage is considered one of the longest barrage in Iraq, with a length of 550 m and consisting of 56 gates. Design drainage of barrages is 6000 m 3 / sec, where the gates are manually and electrically operated. Al-Kut Barrage was built in 1939. It is considered one of the important barrages in Iraq. The Al-Kut barrage is one of the most important irrigation facilities on the Tigris River, as it controls the water distribution between the governorates of Wasit, Maysan, and Dhi-Qar, and secures irrigation projects on the Garraf River and the Dujaila project. It secures water to irrigate nearly one million and a quarter million acres of arable land ( Figure 2) Hameed, 2018]. This study aims to monitor and calculate the horizontal and vertical changes and deformation of Al-Kut barrage over time using the geodetic data taken from Al-Kut barrage department for diff erent periods to determine the deformation through the diff erences between the observations. In addition, the study of monthly and annual fl ow and discharge rates for several years gives us a clear idea of the sedimentation volume above Al-Kut barrage and its impact on the work and effi ciency of the barrage gates. Deformation due to corrosion, water holding eff ect, and water saturation. Therefore, deformation measurements and analysis require high-precision surveying equipment and analysis of the data to identify and avoid hazards. In addition to studying, the sediments collected at upstream of the barrage over

MATERIAL AND METHODS
The horizontal network for monitoring Al-Kut barrage consists of 12 stations distributed over Al-Kut barrage's body, each station (K8, K9, K10, K11, K12, K13, K14, K15, K16, K17, K18, and K19). As for the known reference points, the coordinates of the horizontal network, they are P2 and P3 ( Figure 3). The vertical network for  Figure 4). For surveying measurements, high-precision instruments were provided, the same as those used in the previous measurements, namely: Leica 1200 (RMS) dual frequency (GPS) receiver accuracy with post-processing (constant and fast constant (phase)) with the standard antenna and Leica DNA 03 digital level. Through the available data for surveying observations of Al-Kut barrage for several years (Table 1 and 2), analyzing and comparing the results, and studying the changes that occurred throughout the study period. Where by studying, analyzing, and calculating the differences in the surveying observations of Al-Kut barrage's body of the horizontal and vertical networks. Then, comparing them with the observations of previous years to calculate and determine the size of the deformation through the observations that give us a clear idea of the actual situation of Al-Kut barrage. Where the monitoring network at Al-Kut barrage consists of two horizontal and vertical networks, and both networks consist of a set of stations that are monitored at different times in order to monitor the deformation. In addition, evaluate if it requires intervention to deal with any deviation in the observations taken and determine the extent of its damage, and then assess the safety and integrity of the infrastructure of the barrage body. Also by taking advantage of the data of annual and monthly discharge rates for a number of years. Moreover, analyzing the data to observe the extent to which the flow rates affect the increase in sedimentation the upstream of Al-Kut barrage. Thus, note the extent of its impact

RESULTS AND DISCUSSION
By calculating the diff erences and fi nding the displacement of stations in the horizontal network of areal observations from 2014 to 2021, it was found that the highest displacement in the horizontal network is 50 mm for the station K10. The lowest displacement is 11 mm for the station K19, while the rest of the displacement values range between that as follows 33, 31, 29, 28, 23, 22, 22, 21, and 13 mm ( Figure 5). As for the vertical network observations, the highest diff erence in elevation was 11 mm for the station K7, while the lowest elevation diff erence was 3 mm for the station K25, and the rest of the diff erences between them ranged as follows 9,9,9,9,9,9,8,7,5,5,4 and 4 mm ( Figure 6). It was noted through the analysis of the surveying data, as  well as through simple differences, that there is a slight deformation in the structure of the barrage that falls within the permissible limits. The presence of some cracks in the walls of the navigational passage and the fish corridor, and arcs of the barrage body require intervention to treat it and reduce its damage. And by studying the results of the annual and monthly discharge rates for a number of years to observe the extent of the impact of the run-off rates on increasing sedimentation at the upstream of Al-Kut barrage (Table 3 and 4), and consequently noting the extent to which it affects the efficiency of the barrage. It was noticed that the monthly discharge rate increased during the year 2018, as it is considered a humid watery year, in which the total discharge was recorded 4604 m 3 /s, and it was the lowest rate recorded in the year 2010, and the total decreased and the discharge reached 3621 m 3 /s. As the monthly water revenue rate reached its highest level for the year 2018 during the month of December, at a rate of 12.1 m 3 /s. While the annual revenue was also recorded at the highest rate during the wet year 2018, which recorded an average of 12.6 m 3 /s. The lowest annual revenue recorded during the year 2010 which amounted to 9.5 m 3 /s. Where the sediment accumulated in the studied sections increased during 2019 by 26% compared to the volume of the accumulated sediments in the studied sections during 2018. It was found that the suspended sediment load in the Tigris waters increased during 2019 compared to the sediment load during 2018.
Finally, the accumulation of sediment affected the left bank of the river on the movements of some gates and put pressure on the other gates, which led to some operational problems at the origin of the barrage (Table 5).

CONCLUSIONS
Dams and barrages are among the most important large facilities in the regulation of water and irrigation. Therefore, monitoring with accurate surveying devices, as well as monitoring sedimentation quantities and rates, also knowing the quantities and samples of sediment, lead to an important and effective role in studying the extent of its impact on the work of the barrage, as well as the efficiency of its gates. The monitoring network in Al-Kut barrage consists of two horizontal and vertical networks. Both networks consist of a set of stations that are monitored at different intervals to monitor the deformation and evaluate the effect of the deformation on the efficiency of Al-Kut barrage if an intervention is needed to maintain any deviation in the observations. It also determines the extent of the damage to the dam body and then conducts an assessment of the integrity of the barrage infrastructure. It was noticed by analyzing the surveying data that there is a slight deformation in the barrage structure with some cracks in the walls of the navigational passage, the fish passage, and in some arcs of the barrage's body, which requires intervention to treat it and reduce its damage in the future, as it was noted through the data of run-off rates, the increase in sedimentation at the upstream of Al-Kut barrage, and consequently noting the extent to which it affects the efficiency of the barrage. It was noticed that the monthly discharge rate increased during the year 2018, as it is considered a humid watery year, in which the total discharge was recorded 4604 m 3 /s, and it was the lowest rate recorded in the year 2010, and the total decreased and the discharge reached 3621 m 3 /s. Where the sediment accumulated in the studied sections increased during 2019 by 26% compared to the volume of the accumulated sediments in the studied sections during 2018. Finally, the accumulation of sediment affected the left bank of the river on the movements of some gates and put pressure on the other gates, which led to some operational problems at the origin of the barrage.