# Hydrological Impact of Ilisu Dam on Mosul Dam; the River Tigris

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## Abstract

**:**

## 1. Introduction

#### 1.1. General

#### 1.2. The Watershed of the Ilisu Dam

^{3}/sec. Declaration et al. [13] concluded that a significant portion of the recommended minimum flow (60 m

^{3}/sec) released from Ilisu during dry years would be diverted via the Cizre Dam. They stated that with full implementation of the Ilisu-Cizre projects, all the summer flow could be diverted before it crosses the international border to Iraq. Based on Bilgen [5] statement, it is likely that inflow to the Mosul Dam will be altered, interrupted and reduced.

## 2. Study Area, Watershed Features and Methodology

#### 2.1. Study Area, Watershed Characteristics and Rainfall Distribution

^{2}(Figure 1). A small part of the study area is in Syria. The “Arc Hydro Tools” of the GIS was applied to delineate watersheds for the three dams (Mosul, Ilisu and Cizre). The “Arc Hydro Tools” via “Terrain Preprocessing” is employed to obtain stream definition, flow accumulation, flow direction and drainage point outlets of the catchments.

_{a}is the weighted average elevation, m (AMSL); E

_{i}is the average DEM for each subdivision, m (AMSL); A

_{i}is the subdivision of ith sub-catchment area, km

^{2}; n is total of sub-catchments. The calculated total watershed area is 50,965 km

^{2}. This watershed was originally designated for the Mosul Dam. Currently, it is divided between the Mosul and Ilisu Dams. The larger part of the divided watershed is allocated for the Ilisu Dam from the hydrological point of view. The total watershed’s area calculated by this study is very close to the watershed’s area calculated by Saleh [26].

_{a}is the average regional precipitation, mm; and P

_{i}is the average regional precipitation of the ith area (between two adjacent isohyetals). The average regional precipitations were 727, 737 and 724 mm for the whole watershed (design watershed), the Mosul Dam watershed, and the Ilisu-Cizre Dams watershed, respectively, (Table 1).

#### 2.2. Inflow Calculations and Statistical Analysis

_{r}) in any year by calculated the probability of exceedance as follows:

_{p}is the probability of exceedance; m is order or rank of the event; and N is number of events (data points). The Weibull method was applied for the monthly flows for the period of record using Equation (3). Graphs of exceedance probability for each month are presented in Figure 3.

^{3}/sec; a is the coefficient of the regression model; b is the exponent of the regression model; and A is the catchment area, km

^{2}.

## 3. Results and Discussion

#### 3.1. Watershed and Precipitation Distribution Analysis

^{2}[26]. This watershed area includes all the watershed of the Tigris River upstream of Mosul Dam. The Mosul Dam watershed area was calculated for this paper using ArcMap GIS is 50,965 km

^{2}(Figure 2). The Mosul Dam watershed area, however, is now reduced by the newly constructed Ilisu Dam. As calculated for this paper, the area contributing flow to the Ilisu Dam is estimated as 37,064 km

^{2}(Figure 4a). It is about 73% of the original Mosul Dam watershed. If both the Ilisu and the Cizre Dams are jointly considered, the total watershed area that will be subtracted from the Mosul Dam watershed increased to 39,847 km

^{2}(Figure 4b).

#### 3.2. Inflow to the Mosul Dam

^{3}/s was recorded in 1993, while a minimum inflow of 64 m

^{3}/s in 1991. The highest monthly mean inflow (for the period of record) is 1493 m

^{3}/s and it is for the month of April, while the lowest monthly average inflow is 128 m

^{3}/s occurred in September. The highest 25% and 75% inflows were 1058 and 1924 m

^{3}/s, respectively, both recorded in April. The lowest 25% and 75% inflows were 98 and 156 m

^{3}/s, respectively, both recorded in September. It can be concluded that the highest and the lowest inflows (for the record period of 30 years) occurred in April and September, respectively. The parameters a and b of Equation (5) were derived for each month based on regression equations of Figure 3, as shown in Table 2.

^{3}/sec; the inflow that is available 95% of the time is about 267 m

^{3}/sec (practically the minimum flow for the period of record). The Mosul Dam has operated well for the last three decades on this inflow. The modelled pre-Ilisu Dam was generated from a regression model (Equation (5)) using 0.019 and 0.013 for the parameters a and b, respectively. These values were derived based on the mean annual inflow for the period of record. The analysis of variance (ANOVA) technique reported the mean, median, 25% and 75% of 552 and 544 m

^{3}/sec, 549 and 509 m

^{3}/sec, 384 and 368 m

^{3}/sec and 624 and 705 m

^{3}/sec, for predicted and observed pre-Ilisu Dam operation, respectively. The t-test of pairwise compression indicated that there is no significant difference between predicted versus observed pre-Ilisu Dam inflow with p-value of 0.886.

^{3}/sec and the flow that will be available 95% of the time is about 61 m

^{3}/sec (represented the minimum flow) (Figure 6). This future minimum inflow is equal to the environmental flow (60 m

^{3}/sec) that is the only flow that Turkey is committed to release post-Ilisu–Cizre operation [13]. However, it is so small that it practically turns Mosul Dam inoperable.

^{3}/sec, and 443, 97 and 409 m

^{3}/sec for pre-Ilisu, generated-post-Ilisu and the predicted by Declaration et al. [13] study, respectively. The pairwise compression using Tukey test indicated that there is a significant difference between generated-post-Ilisu versus post-Declaration-Ilisu inflows with p-value of 0.015. It should be indicated that the Declaration-post Ilisu is a release from the Ilisu Reservoir according to a specific scenario outlined by the authors [13]. This release is quite different from the inflow from the reduced watershed which is the subject matter of this paper. This difference between the two approaches may explain the significant statistical difference between the post-Ilisu flows mentioned earlier. The mean annual cumulative inflow to the Mosul Reservoir in the case of generated-post-Ilisu (this study) is 4.6 bcm: a little more than the dead storage of Mosul Reservoir. This paper findings stress that, unless the two riparian countries (Turkey and Iraq) reach a mutual understating and share the water resources of the Tigris River reasonably, Iraq may face the severe reduction in inflow rates to the Mosul Dam (i.e. the worst scenario flow outlined throughout the paper). The flow that is reliable to the Mosul Dam is only 22% of the observed current flow. Furthermore, the flow adapted by this paper may be less than the environmental flow committed by Turkey (60 m

^{3}/sec) for some months of the year.

## 4. Conclusions

^{2}) will be reduced to about one fifth of the total area. The original Mosul Dam’s watershed area as calculated for this paper is 50,965 km

^{2}. The area contributing flow to the Ilisu Dam as calculated by this paper is about 37,064 km

^{2}. If both Ilisu and Cizre Dams are jointly considered, the total watershed area that will be subtracted from Mosul Dam Watershed is about 39,847 km

^{2}. A point should be clarified regarding the stability dam is that recent information indicates that the dam stability has been improved considerably; that the dam reached its sixth-highest pool of record in April 2019 and showed no signs of distress.

^{3}/sec; the flow that will be available 95% of the time is about 61 m

^{3}/sec. The mean monthly inflow was generated and found, for some months, to be less than the environmental flow committed by Turkey.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

- Rahi, K.A.; Al-Madhhachi, A.T.; Al-Hussaini, S.N. Assessment of surface water resources of eastern Iraq. Hydrology
**2019**, 6, 57. [Google Scholar] [CrossRef] [Green Version] - Al-Madhhachi, A.T.; Al-Mussawy, H.A.; Basheer, M.I.; Abdul-Sahib, A.A. Quantifying Tigris riverbanks stability of southeast Baghdad city using BSTEM. Int. J. Hydrol. Sci. Technol.
**2020**. [Google Scholar] [CrossRef] - Partow, H. The Mesopotamian Marshlands: Demise of an Ecosystem Early Warning and Assessment; Division of Early Warning and Assessment, United Nations Environment Program: Nairobi, Kenya, 2001. [Google Scholar]
- Rahi, K.A.; Halihan, T. Changes in the salinity of the Euphrates River system in Iraq. Reg. Environ. Chang.
**2010**, 10, 27–35. [Google Scholar] [CrossRef] - Bilgen, A. The Southeastern Anatolia Project (GAP) in Turkey: An alternative perspective on the major rationales of GAP. J. Balk. Near East. Stud.
**2019**, 21, 532–552. [Google Scholar] [CrossRef] - Kolars, J. Problems of International River Management: The Case of the Euphrates, 2nd ed.; International waters of the Middle East—from Euphrates–Tigris to Nile; Oxford University Press: London, UK, 1994; pp. 44–94. [Google Scholar]
- Aydin, M.; Ulu, A.; Karaduman, C. CFD Analysis of Ilısu Dam Sluice Outlet. Fırat Univ. Turk. J. Sci. Technol.
**2018**, 13, 119–124. [Google Scholar] - Aydin, M.; Ulu, A.; Karaduman, C. Investigation of aeration performance of Ilısu Dam outlet using two-phase flow model. Appl. Water Sci.
**2019**, 9, 111. [Google Scholar] [CrossRef] [Green Version] - Yalcin, E.; Tigrek, S. Hydropower production without sacrificing environment: A case study of Ilisu Dam and Hasankeyf. Int. J. Water Resour. Dev.
**2016**, 32, 247–266. [Google Scholar] [CrossRef] - Yalcin, E.; Tigrek, S. The Tigris hydropower system operations: The need for an integrated approach. Int. J. Water Resour. Dev.
**2019**, 35, 110–125. [Google Scholar] [CrossRef] - Kitchen, W.H.; Ronayne, M. The Ilisu Dam Environmental Impact Assessment Report: Review and critique. Public Archaeol.
**2002**, 2, 101–116. [Google Scholar] [CrossRef] - Rahi, K.A.; Halihan, T. Salinity evolution of the Tigris River. Reg. Environ. Chang.
**2018**, 18, 2117–2127. [Google Scholar] [CrossRef] - Declaration, B.; Williams, P.B.; Frucht, S.B. A Review of the Hydrologic and Geomorphic Impacts of the Proposed Ilisu Dam. Available online: http://www2.weed-online.org/uploads/PWA_Ilisu_Report.pdf (accessed on 10 March 2016).
- Al-Ansari, N.; Issa, I.E.; Sissakian, V.; Adamo, N.; Knutsson, S. Mystery of Mosul Dam the most dangerous dam in the world: The project. J. Earth Sci. Geotech. Eng.
**2015**, 5, 15–31. [Google Scholar] - Rahi, K.A. Salinity management in the Shatt Al-Arab River. Int. J. Eng. Technol.
**2018**, 7, 128–133. [Google Scholar] [CrossRef] - Mosul, D. Wikipedia. Available online: https://en.wikipedia.org/wiki/Mosul_Dam (accessed on 28 February 2020).
- Al-Taiee, T.M.; Rasheed, A.M. Simulation Tigris River Flood Wave in Mosul City Due to a Hypothetical Mosul Dam Break. Damascus Univ. J.
**2009**, 25, 17–36. [Google Scholar] - Mosul Dam Task Force Declares: Mission Complete, Departs Iraq. Mosul Dam Task Force Program Office. Available online: https://www.defensemedianetwork.com/stories/mosul-dam-task-force-declares-mission-complete-departs-iraq/ (accessed on 27 February 2020).
- Bosshard, P.; Declaration, B. Ilisu–a Test Case of International Policy Coherence. Available online: https://www.rivernet.org/turquie/ilisu.htm (accessed on 5 May 2019).
- Yihdego, Y.; Webb, J.A. An empirical water budget model as a tool to identify the impact of land-use change in stream flow in southeastern Australia. Water Resour. Manag. J.
**2013**, 27, 4941–4958. [Google Scholar] [CrossRef] - Yihdego, Y.; Webb, J.A. Assessment of wetland hydrological dynamics in a modified catchment basin: Case of Lake Buninjon, Victoria, Australia. Water Resour. Manag. J.
**2017**, 89, 144–154. [Google Scholar] [CrossRef] - Yihdego, Y.; Khalil, A.; Salem, S.H. Nile River’s Basin Dispute: Perspectives of the Grand Ethiopian Renaissance Dam (GERD). Glob. J. Hum. Soc. Sci.
**2017**, 17, 1–21. [Google Scholar] - Yihdego, Y.; Reta, G.; Becht, R. Human impact assessment through a transient numerical modelling on The UNESCO World Heritage Site, Lake Navaisha, Kenya. Environ. Earth Sci.
**2017**, 76, 9. [Google Scholar] [CrossRef] - Worst-Case. The Merriam-Webster.com Dictionary, Merriam-Webster Inc. Available online: https://www.merriam-webster.com/dictionary/worst-case (accessed on 19 January 2020).
- United States Geological Survey, Earth Explorer (USGS-EE), 2018. Available online: https://earthexplorer.usgs.gov/ (accessed on 5 January 2019).
- Saleh, D.K. Stream Gage Descriptions and Streamflow Statistics for Sites in the Tigris River and Euphrates River Basins, Iraq; US Geological Survey: Reston, VA, USA, 2010.
- United Nations Economic and Social Commission for Western Asia (UN-ESCWA) and Bundesanstalt für Geowissenschaften und Rohstoffe (BGR). Chapter 3: Tigris River Basin. In Inventory of Shared Water Resources in Western Asia; UN-ESCWA: Beirut, Lebanon, 2013. [Google Scholar]
- Barnard, R.W.; Perera, C.; Surles, J.G.; Trindade, A.A. The linearly decreasing stress Weibull (LDSWeibull): A new Weibull-like distribution. J. Balk. Near East. Stud.
**2019**, 6, 11. [Google Scholar] [CrossRef] - Jennings, M.E.; Thomas, W.O.; Riggs, H.C. Nationwide summary of U.S. In Geological Survey Regional Regression Equations for Estimating Magnitude and Frequency of Floods for Ungaged SITES; USGS Water-Resources Investigations Report: Washington, VA, USA, 1994. [Google Scholar]
- Abbas, M.N.; Al-Madhhachi, A.T.; Esmael, S.A. Quantifying soil erodibility parameters due to wastewater chemicals. Int. J. Hydrol. Sci. Technol.
**2019**, 9, 550–568. [Google Scholar] [CrossRef] - Al-Husseini, T.R.; Al-Madhhachi, A.T.; Hasan, M.B. Laboratory experiments and numerical model of local scour around submerged sharp crested weir. J. King Saud Univ. Eng. Sci.
**2020**, 32, 167–176. [Google Scholar] [CrossRef] - Al-Madhhachi, A.T.; Mutter, G.M.; Hasan, M.B. Predicting Mechanistic Detachment Model due to Lead-Contaminated Soil Treated with Iraqi Stabilizers. KSCE J. Civil Eng.
**2019**, 23, 2898–2907. [Google Scholar] [CrossRef]

**Figure 1.**Study area and location of Mosul, Cizre and Ilisu Dams and the digital elevation model (DEM) of the studied watersheds.

**Figure 2.**The Mosul Dam watershed prior to the initiation of Cizre and Ilisu Dams and characteristics of terrain slope of study area. This is the designed watershed as of 1986.

**Figure 3.**Observed annual inflow frequency curves for each month: (

**a**) From October to March and (

**b**) From April to September (for the years 1987−2016).

**Figure 4.**Reduction on the Mosul Dam watershed; (

**a**) in presence of the Ilisu Dam and (

**b**) in presence of the Cizre and Ilisu Dams.

**Figure 6.**The annual inflow to the Mosul Dam Reservoir; the pre-Ilisu operation is the observed inflow for the last 30 years; the generated post-Ilisu operation is the inflow regime predicted by this study after the full operation of the Ilisu and Cizre Dams; and the modeled pre-Ilisu operation (Equation (5)).

**Figure 7.**Reduction Mean monthly inflow to the Mosul Dam; The pre-Ilisu is the observed inflow for the last 30 years; The generated- post-Ilisu is the mean monthly inflow following the operation of Ilisu and Cizre Dams as predicted by this paper; The the mean monthly inflow following the operation of Ilisu and Cizre Dams as predicted by Declaration et al. [13].

**Table 1.**Digital elevation model (DEM) and annual precipitation isolated for catchment areas that proposed in this study.

Digital Elevation Model (DEM), m (AMSL) | Area of the Original Watershed, km^{2} | Total Catchment Area, km^{2} | |
---|---|---|---|

Mosul Watershed | Cizre and Ilisu Watersheds | ||

254–796 | 14980 | 4816 | 10164 |

797–1221 | 16779 | 1986 | 14793 |

1222–1743 | 8679 | 2213 | 6466 |

1744–2330 | 6249 | 1210 | 5039 |

2331–3622 | 4278 | 893 | 3385 |

Total km2 | 50965 | 11118 | 39847 |

Average DEM, m (AMSL) | 1239 | 1164 | 1260 |

Annual Precipitation Isolated, mm | |||

601–700 | 28363 | 4411 | 23952 |

701–800 | 8547 | 3718 | 4829 |

801–900 | 11487 | 2989 | 8498 |

901–1000 | 2569 | 0 | 2569 |

Total km^{2} | 50965 | 11118 | 39847 |

Average precipitation, mm | 727 | 737 | 724 |

**Table 2.**Details of statistical description and regression analysis for observed inflow data of years (1987−2016) for the Mosul Dam Reservoir (N = 30).

Statistical Description | Oct | Nov. | Dec. | Jan. | Feb. | March | April | May | June | July | Aug. | Sept. |
---|---|---|---|---|---|---|---|---|---|---|---|---|

Mean (m3/sec) | 159 | 283 | 402 | 486 | 648 | 985 | 1493 | 1163 | 499 | 231 | 153 | 128 |

Std. Dev. | 55 | 162 | 316 | 305 | 306 | 392 | 638 | 619 | 268 | 99 | 58 | 37 |

Maximum (m3/sec) | 357 | 690 | 1665 | 1330 | 1265 | 2222 | 3275 | 3260 | 1329 | 584 | 298 | 195 |

Minimum (m3/sec) | 78 | 95 | 122 | 156 | 194 | 360 | 502 | 345 | 160 | 77 | 59 | 64 |

Median (m3/sec) | 148 | 244 | 323 | 417 | 629 | 956 | 1332 | 1023 | 445 | 233 | 141 | 124 |

25% | 120 | 163 | 217 | 238 | 388 | 665 | 1058 | 749 | 368 | 156 | 106 | 98 |

75% | 179 | 365 | 470 | 736 | 944 | 1191 | 1924 | 1433 | 590 | 262 | 198 | 156 |

Regression Analysis | ||||||||||||

a | 0.005 | 0.013 | 0.018 | 0.023 | 0.028 | 0.035 | 0.058 | 0.047 | 0.02 | 0.008 | 0.005 | 0.004 |

b | 0.011 | 0.019 | 0.021 | 0.022 | 0.019 | 0.014 | 0.016 | 0.017 | 0.017 | 0.014 | 0.014 | 0.010 |

Coefficient of determination, R^{2} | 0.90 | 0.97 | 0.92 | 0.98 | 0.94 | 0.95 | 0.94 | 0.92 | 0.92 | 0.87 | 0.97 | 0.98 |

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Al-Madhhachi, A.-S.T.; Rahi, K.A.; Leabi, W.K.
Hydrological Impact of Ilisu Dam on Mosul Dam; the River Tigris. *Geosciences* **2020**, *10*, 120.
https://doi.org/10.3390/geosciences10040120

**AMA Style**

Al-Madhhachi A-ST, Rahi KA, Leabi WK.
Hydrological Impact of Ilisu Dam on Mosul Dam; the River Tigris. *Geosciences*. 2020; 10(4):120.
https://doi.org/10.3390/geosciences10040120

**Chicago/Turabian Style**

Al-Madhhachi, Abdul-Sahib T., Khayyun A. Rahi, and Wafa K. Leabi.
2020. "Hydrological Impact of Ilisu Dam on Mosul Dam; the River Tigris" *Geosciences* 10, no. 4: 120.
https://doi.org/10.3390/geosciences10040120