hydrology

Article Assessment of Surface Water Resources of Eastern

Khayyun A. Rahi 1 , Abdul-Sahib T. Al-Madhhachi 2,* and Safaa N. Al-Hussaini 1

1 Department of Environmental Engineering, College of Engineering, Mustansiriyah University, Bab Al Muadham, 10047, Iraq 2 Department of Water Resources Engineering, College of Engineering, Mustansiriyah University, Bab Al Muadham, Baghdad 10047, Iraq * Correspondence: [email protected] or [email protected]; Tel.: +964-771-553-0757

 Received: 16 May 2019; Accepted: 24 June 2019; Published: 26 June 2019 

Abstract: Large amounts of runoff is generated in western and flows into eastern Iraq due to relatively intensive rainstorms along the international border line. Currently, most of this runoff is being wasted by evaporation instead of being stored and preserved for later uses. This paper is an attempt to (1) assess and harness the water resources of eastern Iraq, and (2) propose a storage scheme to use the harvested water in the water shortage times. The runoff of eight catchment areas (Mandali, Qazania, Tursaq, Mirzabad, Galal Badra, al-Chabbab, al-Teeb, and Dwaireeg) is estimated using regression equations derived for areas in the western and southern parts of the United States of America. Several models were selected from two states based on catchment area location, average terrain elevation, average annual precipitation, and slope of main stream. Observed runoffs of Tursaq, Galal Badra, and al-Chabbab streams are analyzed using normal probability plots. Statistical analysis shows that there is no a statistically significant difference between observed and predicted runoffs for different return periods. The study proposes a water reservoir to be constructed within al-Shiwiaja Marsh to accommodate runoff generated within Mandali, Qazania, Tursaq, Mirzabad, and Galal Badra streams. The capacity of the proposed reservoir is 3000 Mm3 and the expected inflow from these streams is projected to exceed the capacity of the reservoir. The proposed reservoir will contribute to the flow of the River Tigris during the non-rainy seasons. More studies are needed to propose and design a storage scheme for two remaining streams (al-Teeb and Dwaireeg).

Keywords: runoffs; streams; water resources of Eastern Iraq; water harvesting; Al-Shiwiaja Marsh

1. Introduction Life could not exist on Earth without water. Water resources seem abundant, but less than one percent of it readily is available for human use. Worldwide water resources are stressed due to ever-increasing demands that are associated with the exponential world population growth. Water for food protection, drinking, and fisheries and environmental protection has been stressed due to world population and economic growth [1]. In arid and semi-arid countries, water shortage problems are more challenging. Water shortage problems are even more challenging in Iraq. Iraq is facing growing water problems due to decrease in recharges of the Euphrates and Tigris and increase in salinity. Rahi and Halihan [2], Rahi and Halihan [3], and Rahi [4] have studied the salinity problems in the Euphrates, the Tigris, and the Shatt al-Arab rivers, respectively. In the three papers, the authors have reached a similar conclusion that Iraq is facing a water shortage crisis and stresses the need to explore all possible water resources to augment the water supplies of the country. Hence, the search for means to overcome water shortages becomes an urgent task.

Hydrology 2019, 6, 57; doi:10.3390/hydrology6030057 www.mdpi.com/journal/hydrology Hydrology 2019, 6, 57 2 of 16

Rainwater harvesting involves a great potential as an innovational and non-conventional water resources. Water harvesting is defined as collection of runoff for its productive use [5]. It can be grouped into two main categories; rainwater harvesting techniques, which harvest runoff from roofs or ground surfaces (sheet flow harvesting); and the other category is flood water harvesting systems, which harvest water from water courses (valleys). Water harvesting systems are mainly implemented in arid and semi-arid zones with annual rainfall ranging from 100–400 mm where rain-fed agriculture could not be sustained. Groundwater potential assessment along with watershed management and environmental assessment can be performed with respect to the geographic characteristics of a drainage basin [6]. Various parameters of the stream and its drainage such as water quality index, pollution index, and metal index can be used to estimate the watershed behavior throughout heavy rainfalls [7,8]. Iraq is located within the northern temperate zone with high semi-stable air pressure and a semi-continental climate affected by the Mediterranean climate [9,10]. The climate of Iraq is characterized by a long hot summer and a short cold winter. Winter is characterized by the movement of south-east warm rainfall producing fronts. In summer, Iraq is affected by hot winds, especially on the southern and central parts causing high temperatures. January is the coldest month with a mean daily temperature ranges from 3 ◦C to 12 ◦C, while July is the warmest month with a mean daily temperature of 38 ◦C. Temperature in the summer can reach as high as 50 ◦C[9]. Several local studies had been performed to analyze the morphometric properties of some parts of the Iraqi lands [6,8,11–17]. Zakaria et al. [11] studied the possibility of using macro rain water-harvesting techniques in irrigation in northern , northwest of Iraq. Their results showed the harvesting of significant amounts of runoff ranging between 0.6 million cubic meters (Mm3) and 42.4 Mm3 annually. The harvested runoff can be used as supplementary crops irrigation. Hassan et al. [12] studied the morphometric properties of Bulkana area, northeast of Iraq. The authors found that the basin of Bulkana has an approximately circular-shaped basin with low drainage density. Malik et al. [6] used remote sensing and the geographic information system (GIS) techniques in analyzing the morphometric properties of al-Chabab river basin in eastern part of Iraq. The authors concluded that there is no real danger of flood at the studied river basin due to rectangular shape of morphometric. Awchi and Kalyana [15] studied the features of drought and its impact on northern of Iraq using GIS techniques. They indicated that the most severe drought periods within the study area were during 1997 to 2001 and 2006 to 2010, with the highest level of drought associated with the northeastern parts of the area. Al-Sudani [8] used Thornthwaite equations to estimate potential and actual evapotranspiration, water balance, and morphometric properties for Basin, eastern of Iraq. They found that water surplus in the basin was 36 mm divided into natural recharge of groundwater and surface runoff in seasonal valleys and rivers. Ali [16] selected a possible site for water harvesting in Badra, eastern Iraq, using GIS techniques. Ali [16] classified the region into three zones based on the suitability for water harvesting: High suitability zone, moderate suitability zone, and low suitability zone. Ibrahim et. al. [17] selected a potential dam site for rainwater harvesting at Dohuk Governorate, northern Iraq, using spatial data to determine the suitability of selected area. More than fifty water courses are flowing from Turkey or Iran into Iraq [18]. Most of their catchment areas are located within these countries. The outflow of these streams depends greatly on annual rainfall rates and watershed characteristics. Rainfall seasons in Iraq are winter and fall. Ninety percent of the rainfall comes between November to April. Few scattered showers may fall in the month of October. In terms of annual rainfall rate, Iraq may be divided into three zones [19]. The first zone is located in the north-east corner of Iraq. The annual rainfall of this zone exceeds 400 mm and agriculture is completely rainfall dependent [4,19]. The second zone, which is the area of interest in this research, is characterized by a rainfall rate of 200–400 mm. This zone extends from Al-Jezerah province, south to southwest of City, to the eastern border strip down to north of City. The third zone is of annual rain of less than 200 mm. This zone includes Baghdad and the rest of the country [10]. Although major valleys flowing from the east are important water suppliers for Iraq, they are unreliable, because no water-sharing agreement existed with Iran. Iran had dammed most of the Hydrology 2019, 6, 57 3 of 16 valleys and cutoff most of the flow to Iraq especially in dry and average water years. Ali [18] has discussed the negative effects on Iraqi water resources resulted by the Iranian actions. On the other hand, in wet water years (for instance, in recent years of 2018–2019), a large volume of runoff flows into Iraq, inundating vast surface area [20]. Therefore, water is flowing into Iraq during extreme floods only when the flow exceeds the storage capacity of the Iranian reservoirs. The importance of these water resources imposes an urgent need to evaluate or quantify the flowing water of the major valleys in eastern Iraq, on Iraqi–Iranian border. This paper is prepared to present a water resources management scheme that includes (1) quantifying the water resources of eastern Iraq for eight catchment areas (Mandali, Qazania, Tursaq, Mirzabad, Galal Badra, al-Chabbab, al-Teeb, and Dwaireeg), and (2) proposing a storage system and a reservoir to use the harvested water during water deficit times. The proposed storage facility will contribute to the flow of the Tigris River during the dry seasons. One of the difficulties in this study is that all the studied watersheds fall within Iran. The geopolitics prevailed in the region make these watersheds not accessible for the needed examinations.

2. Materials and Methods

2.1. Study Area Description The study area is characterized by several, relatively large, peripheral valleys along with numerous smaller ones. Most of these valleys originate within western Iran and flow toward eastern Iraq. The study area is located between (34◦05056”–31◦5902800) N and (45◦2000600–47◦5900200) E. Hydrologically, the study area is integrated (into one main outlet) units containing catchment areas, valleys, and runoff zone. The catchment areas cover about 20,000 km2 located in both Iraq and Iran (Figure1). The Iraqi part of the catchment is mainly flat land. Its elevation ranges from 400 m above mean sea level (a.m.s.l.) at the international border line to about 25 m (a.m.s.l.) at the southeast end of the region. The Iranian part consists of high lands with an elevation of more than 2500 m (a.m.s.l.). It includesHydrology a 2019 series, 6, x of hills and mountain ranges with a basin divide runs along the peaks within4 of 17 Iran.

FigureFigure 1. Location 1. Location map map of of the the study study area of eight eight watersheds watersheds in ineastern eastern Iraq. Iraq.

2.2. Watershed Characteristics The GIS was applied to delineate the eight watersheds. The “Arc Hydro Tools” with “Terrain Preprocessing” were utilized to obtain the flow direction, flow accumulation, stream definition, and drainage point outlets of the watersheds. The watershed was delineated through “Arc Hydro Tools”. Terrain slope area for each watershed was obtained using surface function via “Spatial Analyst Tools”. The slope of main stream for each watershed was calculated based on the differences in terrain elevation and the length of main stream. The hydrological characteristics of eight watersheds are described in Table 1. Mandali watershed has a catchment area of 1246.10 km2, with 7.87 km2 located within Iraq. The drainage outlet is located at 5.45 km northeast of the City of Mandali. Its coordinates are 33°46′52′′N and 45°35′38′′ E (Table 1 and Figure 2). Mandali watershed is in Diyala Government in eastern Iraq. The elevation data from the digital elevation model (DEM) of the Mandali watershed show that elevation ranges from 163 m to 2626 m (a.m.s.l.) with an average of 1101 m (a.m.s.l.). The terrain slope ranges from 7.80 to 71.00 degrees with an average of 12.56 degrees. The total length of the main stream in Mandali watershed was 107 km with an elevation of 163 m to 1313 m (a.m.s.l.). The slope of the main stream (S) in Mandali watershed ranged from 0.009 to 0.013 with an average of 0.011 (Table 1 and Figure 2).

Table 1. Hydrological characteristics of eight watersheds proposed in this study.

Weighted Main Drainage Average Length Catchment Average of Stream Watershed Outlet Terrain of Main Area (A), Terrain Average Names Coordinates, Slope, Stream, km2 Elevation slope (S), DMS Degree km (E), m % 45°35′38′′ E Mandali 12.56 1246.10 1101.26 106.98 0.011 33°46′52′′ N

Hydrology 2019, 6, 57 4 of 16

The major valleys starting from north are Mandali, Qazania, Tursaq, Mirzabad, Galal Badra, al-Chabbab, al-Teeb, and Dwaireeg (Figure1). The first five valleys flood water drains into al-Shuwiaja Marsh. Galal Badra has the largest runoff with a peak runoff of more than 2000 m3/s for the 100-year flood. Al-Chabbab valley flows into the Tigris River downstream of City; its runoff is considered outside al-Shuwiaja Marsh system. The 100-year flood of al-Chabbab valley may reach 800 m3/s (estimated).

2.2. Watershed Characteristics The GIS was applied to delineate the eight watersheds. The “Arc Hydro Tools” with “Terrain Preprocessing” were utilized to obtain the flow direction, flow accumulation, stream definition, and drainage point outlets of the watersheds. The watershed was delineated through “Arc Hydro Tools”. Terrain slope area for each watershed was obtained using surface function via “Spatial Analyst Tools”. The slope of main stream for each watershed was calculated based on the differences in terrain elevation and the length of main stream. The hydrological characteristics of eight watersheds are described in Table1. Mandali watershed has a catchment area of 1246.10 km2, with 7.87 km2 located within Iraq. The drainage outlet is located at 5.45 km northeast of the City of Mandali. Its coordinates are 33◦4605200N and 45◦3503800 E (Table1 and Figure2). Mandali watershed is in Diyala Government in eastern Iraq. The elevation data from the digital elevation model (DEM) of the Mandali watershed show that elevation ranges from 163 m to 2626 m (a.m.s.l.) with an average of 1101 m (a.m.s.l.). The terrain slope ranges from 7.80 to 71.00 degrees with an average of 12.56 degrees. The total length of the main stream in Mandali watershed was 107 km with an elevation of 163 m to 1313 m (a.m.s.l.). The slope of the main stream (S) in Mandali watershed ranged from 0.009 to 0.013 with an average of 0.011 (Table1 and Figure2).

Table 1. Hydrological characteristics of eight watersheds proposed in this study.

Drainage Weighted Average Catchment Length of Main Stream Watershed Outlet Average of Terrain Slope, Area (A), Main Average slope Names Coordinates, Terrain Degree km2 Stream, km (S), % DMS Elevation (E), m 45 35 38” E Mandali ◦ 0 12.56 1246.10 1101.26 106.98 0.011 33◦46052” N 45 43 34” E Qazania ◦ 0 13.77 419.75 746.71 42.51 0.027 33◦34026” N 45 51 18” E Tursaq ◦ 0 12.50 1218.89 980.08 67.15 0.012 33◦29013”N 46 01 59” E Mirzabad ◦ 0 9.24 274.28 722.46 30.44 0.014 33◦24025” N 46 05 56” E Galal Badra ◦ 0 11.70 2306.09 929.01 95.32 0.018 33◦07019” N 46 26 10” E Al-Chabbab ◦ 0 13.38 1275.02 959.47 88.52 0.013 32◦55034” N 47 10 19” E Al-Teeb ◦ 0 11.25 2738.28 800.96 142.52 0.009 32◦25048” N 47 28 44” E Dwaireeg ◦ 0 6.36 3666.90 420.08 206.60 0.005 32◦7034” N

Qazania watershed has a catchment area of 419.75 km2 of which 33.70 km2 is located within Iraq territory. The drainage outlet located at 5.4 km southeast of Finjan Town with coordinates of 45◦4303400 E and 33◦3402600 N (Table1 and Figure2). Qazania watershed is in . The DEM of Qazania watershed ranges from 95 m to 1689 m (a.m.s.l) with an average of 747 m (a.m.s.l.). The terrain slope of Qazania watershed ranges from 8.44 to 72.00 degrees with an average of 13.77 degrees. The total length of the main stream in the watershed is 43 km with elevation of 97 m to 950 m (a.m.s.l.). The slope of the main stream (S) is between 0.014 and 0.042 with an average of 0.027 (Table1 and Figure2). Hydrology 2019, 6, x 5 of 17

45°43′34′′ E Qazania 13.77 419.75 746.71 42.51 0.027 33°34′26′′ N 45°51′18′′ E Tursaq 12.50 1218.89 980.08 67.15 0.012 33°29′13′′N 46°01′59′′ E Mirzabad 9.24 274.28 722.46 30.44 0.014 33°24′25′′ N 46°05′56′′ E Galal Badra 11.70 2306.09 929.01 95.32 0.018 33°07′19′′ N 46°26′10′′ E Al-Chabbab 13.38 1275.02 959.47 88.52 0.013 32°55′34′′ N 47°10′19′′ E Al-Teeb 11.25 2738.28 800.96 142.52 0.009 32°25′48′′ N 47°28′44′′ E Dwaireeg 6.36 3666.90 420.08 206.60 0.005 32°7′34′′ N Qazania watershed has a catchment area of 419.75 km2 of which 33.70 km2 is located within Iraq territory. The drainage outlet located at 5.4 km southeast of Finjan Town with coordinates of 45°43′34′′ E and 33°34′26′′ N (Table 1 and Figure 2). Qazania watershed is in Diyala Governorate. The DEM of Qazania watershed ranges from 95 m to 1689 m (a.m.s.l) with an average of 747 m (a.m.s.l.). The terrain slope of Qazania watershed ranges from 8.44 to 72.00 degrees with an average of 13.77 degrees. The total length of the main stream in the watershed is 43 km with elevation of 97 m to 950 m (a.m.s.l.). The slope of the main stream (S) is between 0.014 and 0.042 with an average of 0.027 Hydrology 2019, 6, 57 5 of 16 (Table 1 and Figure 2). The area of the Tursaq watershed is 1218.90 km2 of which 36.88 km2 is in Iraq. The drainage outletThe located area ofat 7.57 the Tursaqkm northeast watershed of Tursaq is 1218.90 Town km with2 of coordinates which 36.88 of km 45°512 is′ in18 Iraq.′′ E and The 33°29 drainage′13′′N (Tableoutlet located1 and Figure at 7.57 2). km Tursaq northeast watershed of Tursaq is distributes Town with between coordinates Diyala of Governorate 45◦5101800 E andof Iraq 33◦ and29013 Ilam00N Governorate(Table1 and Figure of Iran.2). TursaqThe DEM watershed of the watershed is distributes rang betweenes from Diyala 159 m Governorate to 2565 m (a.m.s.l.) of Iraq and with Ilam an averageGovernorate of 980 of Iran.m (a.m.s.l.). The DEM The of thewatershed watershed slope ranges is 7.74 from to 15975.00 m todegrees 2565 m with (a.m.s.l.) an average with an of average 12.50 degrees.of 980 m The (a.m.s.l.). total length The watershedof the main slope stream is 7.74in th toe watershed 75.00 degrees is 67 withkm with an average an elevation of 12.50 of 159 degrees. m to 1021The totalm (a.m.s.l.). length ofThe the Smain value stream is between in the 0.008 watershed to 0.018 is with 67 km anwith average an elevation of 0.012 (Table of 159 1 m and to 1021Figure m 2).(a.m.s.l.). The S value is between 0.008 to 0.018 with an average of 0.012 (Table1 and Figure2).

Figure 2. Characteristics of terrain elevation, main stream, and terrain slope of Mandali, Qazania,

and Tursaq watersheds.

The area of the Mirzabad watershed is 274.28 km2. It is mostly located in the Iranian side of the international border. The runoff point of the watershed is about 33.55 km northeast of Badra city with coordinates of 46◦0105900 E and 33◦2402500 N (Table1 and Figure3). Mirzabad area is part of of Iraq. The DEM of the watershed ranges from 275 m to 1862 m (a.m.s.l.) with an average of 723 m (a.m.s.l.). The terrain slope of Mirzabad watershed is between 5.35 degrees and 69.00 degrees with an average of 9.24 degrees. The total length of main stream in the watershed is 30.44 km with a terrain elevation of 277 m to 703 m (a.m.s.l.). The S of the main stream ranges from 0.012 to 0.015 with an average of 0.014 (Table1 and Figure3). Galal Badra is the most important stream in the study area [21]. The total area of its watershed is 2306.09 km2. A small fraction of the watershed area (24.39 km2) is located in Iraq; the rest is within the Iranian territory. The drainage outlet is 15 km to the east of Badra City with coordinates of 46◦0505600 E and 33◦0701900 N (Table1 and Figure3). Galal Badra area is within Wasit Governorate of Iraq. The DEM of the watershed ranges from 115 m to 2724 m (a.m.s.l.) with an average of 929 m (a.m.s.l.). The terrain slope ranges from 6.80 to 77.00 degrees with an average of 11.70 degrees. The total length of the main stream is 95.32 km with an elevation of 118 m to 1837 m (a.m.s.l.). The slope (S) of the main stream is between 0.006 and 0.024 with an average of 0.018 (Table1 and Figure3). Al-Chabbab watershed area is 1275.02 km2, nearly all of its falls in Iran territory. The drainage outlet is located at 3.75 km northwest of Bagsaya Town with coordinates of 46◦2601000 E and 32◦5503400 N (Table1 and Figure3). Al-Chabbab area is within Wasit Governorate of Iraq. The DEM of the Hydrology 2019, 6, x 6 of 17

Figure 2. Characteristics of terrain elevation, main stream, and terrain slope of Mandali, Qazania, and Tursaq watersheds.

The area of the Mirzabad watershed is 274.28 km2. It is mostly located in the Iranian side of the international border. The runoff point of the watershed is about 33.55 km northeast of Badra city with coordinates of 46°01′59′′ E and 33°24′25′′ N (Table 1 and Figure 3). Mirzabad area is part of Wasit Governorate of Iraq. The DEM of the watershed ranges from 275 m to 1862 m (a.m.s.l.) with an average of 723 m (a.m.s.l.). The terrain slope of Mirzabad watershed is between 5.35 degrees and 69.00 degrees with an average of 9.24 degrees. The total length of main stream in the watershed is 30.44 km with a terrain elevation of 277 m to 703 m (a.m.s.l.). The S of the main stream ranges from 0.012 to 0.015 with an average of 0.014 (Table 1 and Figure 3). Galal Badra is the most important stream in the study area [21]. The total area of its watershed is 2306.09 km2. A small fraction of the watershed area (24.39 km2) is located in Iraq; the rest is within the Iranian territory. The drainage outlet is 15 km to the east of Badra City with coordinates of 46°05′56′′ E and 33°07′19′′ N (Table 1 and Figure 3). Galal Badra area is within Wasit Governorate of Iraq. The DEM of the watershed ranges from 115 m to 2724 m (a.m.s.l.) with an average of 929 m (a.m.s.l.). The terrain slope ranges from 6.80 to 77.00 degrees with an average of 11.70 degrees. The total length of the main stream is 95.32 km with an elevation of 118 m to 1837 m (a.m.s.l.). The slope (S) of the main stream is between 0.006 and 0.024 with an average of 0.018 (Table 1 and Figure 3). Al-Chabbab watershed area is 1275.02 km2, nearly all of its falls in Iran territory. The drainage Hydrology 2019, 6, 57 6 of 16 outlet is located at 3.75 km northwest of Bagsaya Town with coordinates of 46°26′10′′ E and 32°55′34′′ N (Table 1 and Figure 3). Al-Chabbab area is within Wasit Governorate of Iraq. The DEM of the watershed rangesranges fromfrom 110 110 m m to to 2790 2790 m m (a.m.s.l.), (a.m.s.l.), with with an averagean average of 960 of m960 (a.m.s.l.). m (a.m.s.l.). The terrainThe terrain slope sloperanges ranges from 8.66from to 8.66 73.00 to degrees73.00 degrees with an with average an av oferage 13.38 of degrees. 13.38 degrees. The total The length total oflength the main of the stream main streamis 88.52 is km 88.52 with km an with elevation an elevation of 112 m of to 112 1330 m mto (a.m.s.l.).1330 m (a.m.s.l.). The slope The (S) slopeof the (S) main of the stream main is stream between is between0.006 and 0.006 0.019 and with 0.019 an average with an ofaverage 0.013 (Table of 0.0131 and (Table Figure 1 and3). Figure 3).

Figure 3. Characteristics of terrain elevation, main stream, and terrain slope of Mirzabad, Galal Badra, and al-Chabbab watersheds.

The total area of al-Teeb watershed is 2738.28 km2, mostly located within Iran territory. The drainage outlet located at 45.67 km east of Ali al-Gharbi City with coordinates of 47◦1001900 E and 32◦2504800 N (Table1 and Figure4). Al-Teeb area is part of Maysan Governorate of Iraq. The DEM of the watershed ranges from 53 m to 2494 m (a.m.s.l.), with an average of 801 m (a.m.s.l.). The terrain slope of the watershed ranges from 6.22 to 72.00 degrees with an average of 11.25 degrees. The total length of the main stream is 142.52 km with an elevation between 54 m and 1366 m (a.m.s.l.). The slope (S) of the main stream ranges from 0.003 to 0.016 with an average of 0.009 (Table1 and Figure4). The Dwaireeg watershed has a catchment area of 3666.90 km2, most of which falls within the Iranian territory. The drainage outlet is located at 45.11 km to northeast of the City of Amara with coordinates of 47◦2804400 E and 32◦703400 N (Table1 and Figure4). Dwaireeg area is located in Maysan Governorate of Iraq. The DEM of the watershed ranges from 14 m to 2195 m (a.m.s.l.) with an average of 420 m (a.m.s.l.). The terrain slope (S) of ranges from 2.45 to 72.00 degrees with an average of 6.36 degrees. The total length of the main stream is 206.60 km with an elevation of 18 m to 1185 m (a.m.s.l.). The slope (S) of the main stream ranges from 0.001 to 0.013 with an average of 0.005 (Table1 and Figure4). The values of catchment area (A), average DEM (E), and slope of the main stream (S) in Table1 of eight watersheds are used to predict the flow rate (runoffs) of these watersheds using regression equations adopted by the United States Geological Survey (USGS) for ungagged sites, as discussed in the next section. The flow rates of eight catchment areas are estimated using regression equations from Hydrology 2019, 6, 57 7 of 16 similar areas in the western and southern parts of the United States of America (USA). The regression equations to predict runoffs for the ungagged stations are applied because they need fewer parameters and due to geopolitics prevailed in the region that make the studied watersheds not accessible for detailed examinations. The estimated flow rates are compared with observed runoffs of Tursaq, Galal HydrologyBadra, and 2019 al-Chabbab, 6, x watersheds according to data availability. 8 of 17

FigureFigure 4. 4. CharacteristicsCharacteristics of terrain of terrain elevation, elevation, main stre mainam, stream, and terrain and slope terrain of al-Teeb slope of and al-Teeb Dwaireeg and watersheds.Dwaireeg watersheds.

2.3.2.3. Precipitation Precipitation and and Runoff Runoff CalculationsCalculations WinterWinter andand fallfall are are the the rainy rainy seasons seasons in Iraq in Iraq and Iran.and Iran. Ninety Ninety percent percent of the rainfallof the comesrainfall between comes betweenNovember November to April to with April few with scattered few scattered showers shower fall ins fall October. in October. The average The average annual annual rainfall rainfall was wasacquired acquired from from Iraq Iraq meteorological meteorological organization organization and and seismology seismology [9] and[9] and World World Weather Weather Online Online [22]. [22].Average Average annual annual rainfall rainfall of Galal of Galal Badra Badra was obtained was obtained from Al-Shamaa from Al-Shamaa and Ali’s and [21 Ali’s] study. [21] Tablestudy.2 Tableshows 2 theshows average the average annual rainfallannual forrainfall some for metrological some metrological stations within stations the within eight watershedsthe eight watersheds in eastern inIraq, eastern on the Iraq, Iraqi–Iranian on the Iraqi–Iranian border, from border, October from of 1995 October to March of 1995 of 2019. to March Data ofof average2019. Data annual of average rainfall annualfor the yearsrainfall 1995 for to the 2009 years are missing1995 to in2009 some are of mi thesessing watersheds. in some of The these average watersheds. annual The precipitation average annual(P) in the precipitation last row of Table (P) in2 is the used last to row estimate of Table the flow 2 is rate used of theto estimate eight watersheds. the flow Asrate anticipated of the eight by watersheds.Al-Madhhachi As etanticipated al.’s [20] study, by Al-Madhhachi large amounts et ofal.’s rainfall [20] study, in 2018–2019 large amounts seasons fellof rainfall in Iraqi–Iranian in 2018– 2019borders seasons on these fell in watersheds Iraqi–Iranian due borders to global on warming these watersheds phenomena. due to global warming phenomena. TheThe runorunoffsffs for for each each of theof studiedthe studied streams streams (locally (loc calledally valleys)called valleys) were calculated were calculated using regression using regressionequations adoptedequations by adopted the USGS by [23 the]. TheseUSGS equations [23]. These were equations developed were to estimatedeveloped magnitude to estimate and magnitudefrequency ofand floods frequency for given of floods areas for in given the USA. areas The in the USGS USA. has The developed USGS has regression developed equations regression to equationsestimate the to flowestimate rate the and flow frequency rate and of floodsfrequency in ungagged of floods stations in ungagged for every stations state infor the every USA. state States in thewere USA. divided States into were specific divided hydrological into specific areas, hydrological and for each areas, area a setand of for equations each area were a set produced. of equations After werethorough produced. examination After ofthorough these equations, examination six sets of ofth theseese equations, regression six equations sets of (from these Arizona regression and equations (from Arizona and Texas) are applied to the study area streams based on hydrological and meteorological similarities between these streams and the ones in the USA, where the equations were developed. Three set of equations were selected from each state based on catchment area (A), average DEM (E), average annual precipitation (P), and slope of the main stream (S). The regression equations developed for these hydrologic regions are designed to estimate peak runoffs for return periods of 2, 25, and 100 years. The selected equations from Arizona regions are listed below [23]:

Hydrology 2019, 6, 57 8 of 16

Texas) are applied to the study area streams based on hydrological and meteorological similarities between these streams and the ones in the USA, where the equations were developed. Three set of equations were selected from each state based on catchment area (A), average DEM (E), average annual precipitation (P), and slope of the main stream (S). The regression equations developed for these hydrologic regions are designed to estimate peak runoffs for return periods of 2, 25, and 100 years. The selected equations from Arizona regions are listed below [23]:

0.433 Q2 = 87.0A (a) 0.487 Q25 = 586.0A (b) (1) 0.499 Q100 = 1100.0A (c)

0.673 0.605 1.03 Q2 = 5.66A E− P (a) 0.626 1.14 0.944 Q25 = 186.0A E− P (b) (2) 0.610 1.30 0.915 Q100 = 553A E− P (c)

0.555 Q2 = 96.6A (a) 0.471 Q25 = 685.0A (b) (3) 0.447 Q100 = 1230.0A (c)

Table 2. The annual average rainfall (mm) for some metrological stations within the eight watersheds in eastern Iraq, on the Iraqi–Iranian border [9,21,22].

Watershed Names Mandali Qazania Tursaq Mirzabad Galal Badra Al-Chabbab Al-Teeb Dwaireeg 1995 - - - - 345.0 109.0 198.0 - 1996 - - - - 218.4 124.1 220.0 - 1997 - - - - 217.4 83.4 183.2 - 1998 - - - - 269.3 103.9 105.8 - 1999 - - - - 243.1 130.6 130.0 - 2000 - - - - 179.1 090.8 096.1 - 2001 - - - - 245.6 093.1 100.3 - 2002 - - - - 233.3 091.3 134.6 - 2003 - - - - 160.1 124.4 - - erent years, mm

ff 2004 - - - - 175.4 125.1 - - 2005 - - - - 151.3 092.4 - - 2006 - - - - 234.7 188.4 - - 2007 - - - - 124.0 040.1 - - 2008 - - - - 195.7 109.0 - - 2009 106.8 035.9 159.4 035.2 112.1 051.4 035.2 191.9 2010 251.4 125.4 232.3 040.7 108.0 084.0 040.7 262.5 2011 096.1 095.2 262.8 054.2 128.6 094.2 054.2 270.3 2012 090.6 090.6 201.3 043.3 158.4 056.6 043.4 206.0 2013 149.6 181.7 213.8 240.9 290.4 156.1 188.6 284.3 Annual Precipitation for di 2014 166.2 174.2 182.2 190.2 198.2 130.2 053.7 260.8 2015 066.8 084.6 102.5 110.3 138.1 110.2 060.3 071.0 2016 104.4 147.9 191.4 224.9 278.4 160.9 079.7 095.4 2017 111.4 115.1 138.7 152.3 165.9 073.3 062.8 159.4 2018 138.8 138.7 265.7 039.5 265.3 074.9 037.6 121.2 2019 894.4 894.2 1142.1 451.7 1139.9 423.5 451.7 809.8 Average precipitation 197.9 189.4 281.1 143.9 239.0 116.8 119.8 248.4 (P), mm

The selected equations from Texas regions are listed below [23]:

0.540 Q2 = 175.0A (a) 0.616 Q25 = 759.0A (b) (4) 0.638 Q100 = 1175.0A (c) Hydrology 2019, 6, 57 9 of 16

0.629 0.13 Q2 = 89.9A S (a) 0.747 0.386 Q25 = 144.0A S (b) (5) 0.788 0.469 Q100 = 157.0A S (c)

Q = 49.8A0.602(P 4)0.447 (a) 2 − Q = 150.0A0.692(P 4)0.608 (b) (6) 25 − Q = 216.0A0.725(P 4)0.647 (c) 100 − 3 where Q2, Q25, and Q100 are peak discharges for 2-, 25-, and 100-year return period, respectively, ft /s; A is the catchment areas, mile2; E is the mean catchment elevation in thousands of feet; P is the mean annual precipitation, inches; and S is slope of main channel of watershed, feet/mile. The values of A, E, and S were obtained from Table1 while the values of P were obtained from Table2. All calculated discharges were converted to m3/s.

2.4. Data Analysis The Ministry of Water Resources in Iraq provided observed flow rates of three streams in this study. They are Tursaq, Galal Badra, and al-Chabbab. No sufficient observed data were provided for the other streams and watersheds. The observed flow data are for the period of March 2001 to December 2018. The maximum flow rate of 2050 m3/s was recorded in the Galal Badra stream in November of 2018. There are several probability distributions to describe the observed data for annual peak flow estimations such as long-normal, Pearson Type III, Gumbel’s extreme values, normal probability plots, and others. The normal probability distribution was selected because it gave reasonable fit to the observed flow data. The statistical analyses implemented in this paper are similar to the analyses used by the USGS to examine streamflow for several gagging stations on the Euphrates and Tigris rivers [24]. Due to limited spatial and temporal availability of observed flow rate data for the streams of the study area, the streamflow formulas were not derived for Tursaq, GalaBadra, and al-Chabbab streams. The computed statistical differences in regression equations adopted by USGS for Arizona and Texas regions are also investigated using the analysis of variance (ANOVA) technique within SigmaPlot 12.5 Software (Systat Software Inc., San Jose, CA, USA). The Software includes several statistical analyses to treat the groups of data such as; descriptive statistics, one-way ANOVA, two-way ANOVA, three-way ANOVA, and others. A one-way ANOVA is recommended by SigmaPlot 12.5 Software to describe and compare the data with basic statistics for data with more than two groups. Therefore, a one-way ANOVA reported the mean and median in this study for Equations (1a) through (6c). The pairwise comparison of t-tests in SigmaPlot 12.5 Software has several tests such as; Tukey test, student–Newman–Keuls, Dunnett test, Bonferroni test, and others. The software recommended both Tukey test method and student–Newman–Keuls method to test all pairwise comparisons of the mean responses to different treatment groups. Thus, in this study, pairwise comparisons of t-tests are calculated for both observed and predicted flow rates using the Tukey test method and student–Newman–Keuls method, which revealed a significant difference compared to ANOVA with a significance level of α = 0.05 [25]. Water harvesting is the collection of runoff for productive purposes. Instead of runoff being left to cause erosion, the water could be harvested and utilized. Of course, in a year of severe drought there may be no runoff to collect, but an efficient water harvesting system will improve plant growth in the majority of years [5]. Water harvesting may be divided into two broad categories; roof-top rainwater harvesting and sheet flow (or flood) water harvesting. In this study, the suitable water harvesting technique is the flood harvesting technique. The study area is known for its sheet flow and valley flow. The collected water from Mandali, Qazania, Tursaq, Mirzabad, and Galal Badra streams should be diverted to al-Shiwiaja Marsh for future use in populated areas, such as the towns of Badra, Mandli, and Jassan. It is suggested that the details and designs of the water harvesting scheme are performed for each site independent of other areas or projects. The cultural and population needs are important factors to be considered by the planners and designers. Hydrology 2019, 6, x 11 of 17

3. Results

3.1. Predicted Versus Observed Runoffs Based on Equations (1a) through (3c), Figure 5 shows a comparison of estimated peak runoffs of eight watersheds for the return period of 2, 25, and 100 years. For the two-year return period, the mean values of estimated runoffs are 37.74, 58.60, and 92.23 m3/s for Equations (1a), (2a), and (3a), respectively. A one-way ANOVA test for analysis of variance between Equations (1a), (2a), and (3a) shows that there is a statistically significant difference between Equations (3a) versus (1a) and (2a) (with p-value < 0.001) (Figure 5a). Meanwhile, there was no significant differences between Equations (1a) versus (2a) with a p-value equal to 0.257. For the 25-year return period, the median values of estimated runoffs were 337.80, 497.93, and 357.65 m3/s for Equations (1b), (2b), and (3b), respectively. There is a statistically significant difference between Equations (1b) versus (2b) and (3b) (with p-value < 0.001) for estimated runoffs (Figure 5b). No statistically significant differences were observed between estimated runoffs of Equations (2b) versus (3b). There is a statistically significant difference between estimated runoffs using Equations (1c), (2c), and (3c) with a p-value less than 0.001, for the 100-year return period. The median values of estimated runoffs were 682.96, 1062.07, 3 Hydrologyand 553.572019 ,m6, 57/s for Equations (1c), (2c), and (3c), respectively (Figure 5c). 10 of 16 Figure 6 shows a comparison of estimated runoffs of eight watersheds based on Equations (4a) through (6c) that selected from taxes regions for the peak runoffs of the 2-, 25-, and 100-year return 3.periods. Results The mean values of estimated runoffs were 151.57, 234.91, and 109.31 m3/s for Equations (4a), (5a), and (6a), respectively, for the two-year return period. ANOVA test for analysis of variance 3.1. Predicted Versus Observed Runoffs shows that there is a statistically significant difference between Equations (5a) versus (4a) and (6a) (withBased p-value on Equations < 0.001) (1a)(Figure through 6a). (3c),Meanwhile, Figure5 showsthere were a comparison no significant of estimated differences peak runobetweenffs ofEquations eight watersheds (4a) versus for the(6a) returnwith a period p-value of 2,equal 25, andto 0.094. 100 years. For the For 25 the-year two-year return return period, period, there theis a meanstatistically values significant of estimated difference runoffs are between 37.74, 58.60,Equations and 92.23(4b), m(5b),3/s forand Equations (6b) (with (1a), p-value (2a), andless (3a),than respectively.0.001) (Figure A 6b). one-way The median ANOVA values test for of analysisestimated of runoffs variance of betweenthe 25-year Equations return period (1a), (2a), were and 971.99, (3a) shows2073.25, that and there 311.36 is a statistically m3/s for Equations significant (4b), diff erence(5b), and between (6b), Equationsrespectively. (3a) There versus is (1a) not and a statistically (2a) (with psignificant-value < 0.001) difference (Figure between5a). Meanwhile, Equations there (4c) wasversus no (6c) significant of the 100-year di fferences return between period Equations with a p-value (1a) versusequal (2a)to 0.545. with aThep-value median equal values to 0.257. of estimated For the 25-year runoffs return of the period, 100-ye thear return median period values were of estimated 1926.64, runo4592.45,ffs were and 337.80, 1410.51 497.93, m3/s for and Equations 357.65 m3 /(4c),s for (5c), Equations and (6c), (1b), respectively (2b), and (3b), (Figure respectively. 6c). In general, There is the a statisticallyresults from significant Figures 5 di andfference 6 show between that Equationsthe set of equations (1b) versus with (2b) andthe parameters (3b) (with p -valueaverage< 0.001)DEM for(E), estimatedcatchment runo areaffs ( (FigureA), and5b). average No statistically annual precipitation significant di (ffPerences), reasonably were observed predicted between the flow estimated rates of runoeightff swatersheds of Equations (such (2b) versusas the (3b). set Thereof Equations is a statistically (2), (4), significant and (6)) diforfference different between return estimated periods. runoMeanwhile,ffs using the Equations set of equations (1c), (2c), and(such (3c) as withset of a Equationp-value less (5)) than that 0.001,included for thethe 100-yearparameter return slope period. of the Themain median stream values (S) did of not estimated reasonably runo ffpredicts were the 682.96, flow 1062.07, rates of andstudied 553.57 wate m3rsheds/s for Equations for different (1c), return (2c), andperiods. (3c), respectively (Figure5c).

FigureFigure 5. 5.Comparison Comparison of of estimated estimated runo runoffsffs using using empirical empirical equations equations of of Arizona Arizona regions regions adopted adopted by by UnitedUnited States States Geological Geological Survey Survey (USGS) (USGS) for the for eight the watershedseight watersheds of: (a) 2-yearof: a) return2-year period, return ( bperiod,) 25-year b) return25-year period, return and period, (c) 100-year and c) 100-year return period. return period.

Figure6 shows a comparison of estimated runo ffs of eight watersheds based on Equations (4a) through (6c) that selected from taxes regions for the peak runoffs of the 2-, 25-, and 100-year return periods. The mean values of estimated runoffs were 151.57, 234.91, and 109.31 m3/s for Equations (4a), (5a), and (6a), respectively, for the two-year return period. ANOVA test for analysis of variance shows that there is a statistically significant difference between Equations (5a) versus (4a) and (6a) (with p-value < 0.001) (Figure6a). Meanwhile, there were no significant di fferences between Equations (4a) versus (6a) with a p-value equal to 0.094. For the 25-year return period, there is a statistically significant difference between Equations (4b), (5b), and (6b) (with p-value less than 0.001) (Figure6b). The median values of estimated runoffs of the 25-year return period were 971.99, 2073.25, and 311.36 m3/s for Equations (4b), (5b), and (6b), respectively. There is not a statistically significant difference between Equations (4c) versus (6c) of the 100-year return period with a p-value equal to 0.545. The median values of estimated runoffs of the 100-year return period were 1926.64, 4592.45, and 1410.51 m3/s for Equations (4c), (5c), and (6c), respectively (Figure6c). In general, the results from Figures5 and6 show that the set of equations with the parameters average DEM (E), catchment area (A), and average annual precipitation (P), reasonably predicted the flow rates of eight watersheds (such as the set of Equations (2), (4), and (6)) for different return periods. Meanwhile, the set of equations (such as set of Equation Hydrology 2019, 6, 57 11 of 16

(5)) that included the parameter slope of the main stream (S) did not reasonably predict the flow rates ofHydrology studied 2019 watersheds, 6, x for different return periods. 12 of 17 Hydrology 2019, 6, x 12 of 17

FigureFigure 6. 6.Comparison Comparison ofof estimatedestimated runorunoffsffs usingusing empiricalempirical equationsequations ofof TaxesTaxes regions regions adopted adopted by by Figure 6. Comparison of estimated runoffs using empirical equations of Taxes regions adopted by USGSUSGS for for the the eight eight watersheds watersheds of: of: (a )a) 2-year 2-year return return period, period, (b b)) 25-year 25-year return return period, period, and and (c )c) 100-year 100-year USGS for the eight watersheds of: a) 2-year return period, b) 25-year return period, and c) 100-year returnreturn period. period. return period. BasedBased on on regression regression analysis analysis using using normal normal probability probability plots plots for for observed observed flow flow rates, rates, Figure Figure7 7 Based on regression analysis using normal probability plots for observed flow rates, Figure 7 reportsreports the the observed observed flow flow rates rates at di atfferent different probability probability of Tursaq, of Tursaq, Galal Badra, Galal andBadra, al-Chabbab and al-Chabbab streams. reports the observed flow rates at different probability of Tursaq, Galal Badra, and al-Chabbab Thestreams. regression The regression analysis produced analysis pproduced-values of p 0.687,-values 0.666, of 0.687, and 0.9040.666, for and Tursaq, 0.904 Galalfor Tursaq, Badra, Galal and streams. The regression analysis produced p-values of 0.687, 0.666, and 0.904 for Tursaq, Galal al-ChabbabBadra, and streams, al-Chabbab respectively. streams, Based respectively. on normal Based probability on normal plots probability of Figure7, theplots return of Figure periods 7, for the Badra, and al-Chabbab streams, respectively. Based on normal probability 3plots of Figure 7, the thereturn 2-, 25-, periods and 100-yearfor the 2-, of 25-, observed and 100-year runoff ofs wereobserved 142.2, runoffs 1418.2, were and 142.2, 1647.7 1418.2, m /s forand Tursaq 1647.7 stream,m3/s for return periods for the 2-, 25-,3 and 100-year of observed runoffs were 142.2, 1418.2, and3 1647.7 m3/s for 392.1,Tursaq 1830.8, stream, and 392.1, 2024.3 1830.8, m /s forand Galal 2024.3 Badra m3/s stream, for Galal and Badra 66.9, stream, 929.7, and and 1103.8 66.9, 929.7, m /s forand al-Chabbab 1103.8 m3/s Tursaq stream, 392.1, 1830.8, and 2024.3 m3/s for Galal Badra stream, and 66.9, 929.7, and 1103.8 m3/s stream,for al-Chabbab respectively. stream, The respectively. selected regression The selected set of Equationsregression (4) set that of adoptedEquations by (4) USGS that toadopted estimate by for al-Chabbab stream, respectively. The selected regression set of Equations (4) that adopted by runoUSGSffs to reasonably estimate runoffs predicted reasonably the observed predicted flow ratesthe observed for the three flow streamsrates for (Tursaq, the three Galal streams Badra, (Tursaq, and USGS to estimate runoffs reasonably predicted the observed flow rates for the three streams (Tursaq, al-Chabbab)Galal Badra, at and the al-Chabbab) 2-, 25-, and 100-yearat the 2-, 25-, return and periods 100-year (Figure return8). periods The observed (Figure and8). The predicted observed flow and Galal Badra, and al-Chabbab) at the 2-, 25-, and 100-year return periods (Figure 8). The observed and ratespredicted of set flow of Equations rates of set (4) of were Equations equivalent (4) were at the equivalent 2- and 100-year at the return2- and periods100-year for return Tursaq periods stream for predicted flow rates of set of Equations (4) were equivalent at the 2- and 100-year return periods for (FigureTursaq8 a),stream at the (Figure 2-year 8a), return at the period 2-year for return Galal Badraperiod streamfor Galal (Figure Badra8b), stream and at(Figure the 2- 8b), and and 25-year at the Tursaq stream (Figure 8a), at the 2-year return period for Galal Badra stream (Figure 8b), and at the return2- and periods 25-year for return al-Chabbab periods stream for (Figureal-Chabbab8c). The stre predictedam (Figure flow 8c). rates The of equationspredicted 2flow and 6rates were of 2- and 25-year return periods for al-Chabbab stream (Figure 8c). The predicted flow rates of equivalentequations 2 to and observed 6 were flowequivalent rates atto theobserved 2-year flow return rates period at the for 2-year Tursaq return and period al-Chabbab for Tursaq streams and equations 2 and 6 were equivalent to observed flow rates at the 2-year return period for Tursaq and (Figureal-Chabbab8a,c). streams (Figure 8a,c). al-Chabbab streams (Figure 8a,c).

Figure 7. Statically analyzed using normal probability plots of observed flow rates for the three streams: Figure 7. Statically analyzed using normal probability plots of observed flow rates for the three (aFigure) Tursaq, 7. (Staticallyb) Galal Badra,analyzed and using (c) al-Chabbab. normal probability plots of observed flow rates for the three streams: a) Tursaq, b) Galal Badra, and c) al-Chabbab. streams: a) Tursaq, b) Galal Badra, and c) al-Chabbab.

Hydrology 2019, 6, 57 12 of 16 Hydrology 2019, 6, x 13 of 17

Figure 8. Comparison between observed and predicted flow rates at the 2-, 25-, and 100-year return periodsFigure for8. Comparison the three streams: between (a) observed Tursaq, (b and) Galal predicted Badra, fl andow (ratesc) al-Chabbab. at the 2-, 25-, and 100-year return periods for the three streams: a) Tursaq, b) Galal Badra, and c) al-Chabbab. A one-way ANOVA test for analysis of variance between observed and predicted runoffs of TursaqA waterone-way course ANOVA shows test that for the analysis mean flow of ratesvariance were between 1069.33, observed 671.44, 925.73, and predicted and 860.71 runoffs m3/s for of observedTursaq water runo courseff, estimated shows runo thatff thefrom mean the flow set of rates Equation were 1069.33, (2), estimated 671.44, runo 925.73,ff from and set 860.71 of Equation m3/s for (4),observed and estimated runoff, estimated runoff from runoff set of from equations the set 6, of respectively. Equation (2), For estimated Galal Badra runo stream,ff from set the of mean Equation flow rates(4), and were estimated 1415.71, 914.32,runoff 1379.64,from set andof equations 1131.58 m 6,3/ srespectively. for observed For flow Galal rates, Badra estimated stream, runo theff frommean Equationflow rates (2), were estimated 1415.71, runo 914.32,ff from 1379.64, Equation and (4), 1131.58 and estimated m3/s for observed runoff from flow Equation rates, estimated (6), respectively. runoff While,from Equation the mean (2), flow estimated rates values runoff of al-Chabbab from Equation stream (4), were and 700.14, estimated 313.96, runoff 952.18, from and Equation 190.10 m 3(6),/s forrespectively. observed flowWhile, rates, the estimated mean flow runo ratesff from values Equation of al-Chabbab (2), estimated stream runo wereff from 700.14, Equation 313.96, (4), 952.18, and estimatedand 190.10 runo m3/sff fromfor observed Equation flow (6), rates, respectively. estimated The runoff results from of statistical Equation analysis (2), estimated confirmed runoff that from the setEquation of Equation (4), and (4) areestimated the best runoff option from to represent Equation the (6), observed respectively. flow rates.The results However, of statistical ANOVA analysis test for analysisconfirmed of variancethat the showsset of thatEquation there is(4) no are statistically the best significantoption to direpresentfference betweenthe observed observed flow runo rates.ff andHowever, empirical ANOVA set Equations test for of (2),analysis (4), and of (6)variance with p -valuesshows ofthat 0.353, there 0.354, is andno statistically 0.063 for Tursaq, significant Galal Badra,difference and between al-Chabbab observed streams, runoff respectively. and empirical set Equations of (2), (4), and (6) with p-values of 0.353, 0.354, and 0.063 for Tursaq, Galal Badra, and al-Chabbab streams, respectively. 3.2. Water Harvesting Techniques and Proposed Reservoir 3.2. Water Harvesting Techniques and Proposed Reservoir The watersheds of Mandali, Qazania, Tursaq, Mirzabad, and Galal Badra discharge through severalThe natural watersheds streams of into Mandali, northern Qazania, and southern Tursaq, parts Mirzabad, of al-Shiwiaja and Galal Marsh Badra (Figure discharge9). The southern through partseveral of al-Shiwiaja natural streams Marsh into is a largenorthern shallow and natural southe depressionrn parts of located al-Shiwiaja 20 km Marsh northeast (Figure of Kut 9). City.The Thesouthern marsh part is very of al-Shiwiaja saline, most Marsh of times, is a and large not sha suitablellow natural for agriculture depression or municipallocated 20 usages.km northeast Its main of functionKut City. is The to accommodate marsh is very flood saline, water most and of rout times, it to and the Tigrisnot suitable River, throughfor agriculture Um al-Jerri or municipal channel. Theusages. northern Its main part function of al-Shiwiaja is to a Marshccommodate is located flood further water north and rout (not it showing to the Tigris in the River, map) andthrough is being Um usedal-Jerri as channel. a natural The collection northern point part for of runoal-Shiwiajaffs from Marsh nearby is streamslocated further (Mandali, north Qazania, (not showing and Tursaq). in the Themap) northern and is partbeing is shallowused as anda natural not fit collection to as a reservoir. point for The runoffs southern from part nearby of al-Shiwiaja streams Marsh (Mandali, has lowestQazania, elevation and Tursaq). of 13 m The (a.m.s.l). northern While, part the is shallow level of 17and m not (a.m.s.l) fit to runsas a reservoir. parallel to The the southern protective part dyke of locatedal-Shiwiaja on southern Marsh has part lowest of al-Shiwiaja elevation Marsh. of 13 Them (a.m.s.l). southern While, al-Shiwiaja the level Marsh of has 17 am surface (a.m.s.l) area runs of 250parallel km2 asto delineatedthe protective by this dyke study. located The estimated on sout capacityhern part of southernof al-Shiwiaja part of Marsh. al-Shiwiaja The assouthern existed isal-Shiwiaja about 1000 Marsh Mm3. has a surface area of 250 km2 as delineated by this study. The estimated capacity of southern part of al-Shiwiaja as existed is about 1000 Mm3.

Hydrology 2019, 6, 57 13 of 16 Hydrology 2019, 6, x 14 of 17

Figure 9. Proposed reservoir of flood water harvesting techniques for Mandali, Qazania, Tursaq, Figure 9. Proposed reservoir of flood water harvesting techniques for Mandali, Qazania, Tursaq, Mirzabad, and Galal Badra watersheds. Mirzabad, and Galal Badra watersheds. Models of flood water harvesting estimates and river trainings using GIS tools are applied to Models of flood water harvesting estimates and river trainings using GIS tools are applied to this research to determine the proposed reservoir. The water harvesting techniques are site- and this research to determine the proposed reservoir. The water harvesting techniques are site- and cultural-specific. The choice of a given technique depends on the type of water harvesting, the goal cultural-specific. The choice of a given technique depends on the type of water harvesting, the goal of the harvesting, and the economic considerations among other factors. The flood water harvesting of the harvesting, and the economic considerations among other factors. The flood water harvesting technique is used to store the flood flows from Mandali, Qazania, Tursaq, Mirzabad, and Galal Badra technique is used to store the flood flows from Mandali, Qazania, Tursaq, Mirzabad, and Galal watersheds to the proposed reservoir (Figure9). According to this proposal, river trainings using GIS Badra watersheds to the proposed reservoir (Figure 9). According to this proposal, river trainings tools are performed to determine the natural water courses (natural proposed channels) (dark blue lines using GIS tools are performed to determine the natural water courses (natural proposed channels) of Figure9). The DEM of the study area is subdivided into three levels: Less than 13 m (a.m.s.l), 13–18 m (dark blue lines of Figure 9). The DEM of the study area is subdivided into three levels: Less than 13 (a.m.s.l), and above 18 m (a.m.s.l).The proposed reservoir (light purple area in Figure9) encompasses m (a.m.s.l), 13–18 m (a.m.s.l), and above 18 m (a.m.s.l).The proposed reservoir (light purple area in the contour line 18 m as the highest storage level and the contour line 13 m as the lowest storage level. Figure 9) encompasses the contour line 18 m as the highest storage level and the contour line 13 m as The surrounding dykes should be constructed along line 18 m to accommodate the highest water the lowest storage level. The surrounding dykes should be constructed along line 18 m to level as well as the required free board. The proposed reservoir includes the present southern part of accommodate the highest water level as well as the required free board. The proposed reservoir al-Shiwiaja Marsh. Total surface area of the proposed reservoir is 590 km2 corresponding to a storage includes the present southern part of al-Shiwiaja Marsh. Total surface area of the proposed reservoir capacity of 3000 Mm3. The total volume of inflow as estimated by this study is 4700 Mm3, which is is 590 km2 corresponding to a storage capacity of 3000 Mm3. The total volume of inflow as estimated higher than the available storage capacity. The flood of 2018–2019 in the study area has confirmed this by this study is 4700 Mm3, which is higher than the available storage capacity. The flood of 2018– finding. The outflow to the Tigris River is through the existing Um al-Jerri and al-Nishama Outlets 2019 in the study area has confirmed this finding. The outflow to the Tigris River is through the (the current combined discharge of both outlets is 75 m3/s). Al-Chabbab stream directly discharges existing Um al-Jerri and al-Nishama Outlets (the current combined discharge of both outlets is 75 into the Tigris River, downstream of Um al-Jerri channel. Future study is planned to present design m3/s). Al-Chabbab stream directly discharges into the Tigris River, downstream of Um al-Jerri details of the proposed reservoir as well as the water harvesting scheme for al-Teeb and Dwaireeg channel. Future study is planned to present design details of the proposed reservoir as well as the watershed regions. Currently, these two streams discharge into the Iraqi southern marshes (such as water harvesting scheme for al-Teeb and Dwaireeg watershed regions. Currently, these two streams al-Hawizeh Marshes). discharge into the Iraqi southern marshes (such as al-Hawizeh Marshes).

4. Discussion Six sets of regression equations adopted from the USGS based on hydrological and meteorological similarities between the streams of the study area and the ones in the USA were used

Hydrology 2019, 6, 57 14 of 16

4. Discussion Six sets of regression equations adopted from the USGS based on hydrological and meteorological similarities between the streams of the study area and the ones in the USA were used to predict the runoffs of the eight watersheds. Outflow rates from each watershed were determined using all selected sets and for return periods of 2, 25, and 100 years. A one-way ANOVA test for analysis of variance between regression equations was conducted to find out about statistical differences. The results from Figures5 and6 showed that the set of Equations (2) (derived for a hydrological region in Arizona), Equations (4), and (6) (both derived for regions in Texas) demonstrated the most reliable results for the three return periods. These regression equations were based on parameters of the average DEM, the catchment area, and the average annual precipitation. Meanwhile, the set of Equation (5) that were based on the parameter slope of the main stream did not reasonably predict the flow rates of the study area. The statistical analysis between observed and predicted runoffs (using sets of Equations (2), (4), and (6)) for Tursaq, Galal Badra, and al-Chabbab streams showed that there is no statistically significant difference between observed runoff and generated flows. The set of Equation (4) based on the parameter catchment area only produced the best option to represent the observed flow rates. Other models and methods to estimate outflow such us the hydrograph or numerical models were not applied because all the studied watersheds fall within Iran; the geopolitics prevailed in the region make these watersheds not accessible for more detailed examinations. A reservoir is proposed to be constructed in a location topography situated to serve five of the eight watersheds (Mandali, Qazania, Tursaq, Mirzabad, and Galal Badra). The reservoir is designated to collect harvested water (generated flow) during the wet seasons and release to the Tigris River during dry seasons. The new reservoir is an expansion of the existed al-Shiwiaja Marsh depression to accommodate about 3000 Mm3; a little less than the generated flow of the five streams. The designated outlets to the Tigris River are Um al-Jerri and al-Nishama with combined disgorge of about 75 m3/s. Al Chabbab stream is already connected to the Tigris River and the study proposed no further improvement for its outlet. More studies are required to address the outflow from al-Teeb and Dwaireeg watersheds.

5. Conclusions Results of this study demonstrate the promising potential of eastern Iraqi area for water resources and harvesting projects. The study area includes eight watersheds: Mandali, Qazania, Tursaq, Mirzabad, Galal Badra, al-Chabbab, al-Teeb, and Dwaireeg. The watersheds are delineated using GIS techniques. The hydrological characteristics, catchment areas, average terrain elevation, average annual precipitation, and slope of main stream of eight watersheds are described in details. The observed flow rates of Tursaq, Galal Badra, and al-Chabbab streams are compared with runoff rates calculated by regression models of the USGS. The results show that the set of equations based on average DEM, catchment area, and average precipitation reasonably predicted the flow rates of eight watersheds for 2-, 25-, and 100-year return periods. The statistical analysis of variance shows that there are no statistically significant differences between the observed and predicted runoff by the regression models for Tursaq, Galal Badra, and al-Chabbab streams based on catchment areas for different return periods. A proposed reservoir located within al-Shiwiaja Marsh could store up to three times the water compared to the current capacity of the marsh. The expected inflow is higher than the capacity of the proposed reservoir. In this study, one major limitation factor is that all of watersheds are located in another country (Iran). They are not accessible to the researchers for necessary examinations. The other limitation is the lack of observed data for most of the studied streams. Due to the complex hydrological nature of the study area, not all the expected inflow was accommodated or accounted for. Future studies are required to provide more details and designs about the proposed reservoir as well as a robust scheme to utilize the waters of al-Teeb and Dwaireeg watersheds. Hydrology 2019, 6, 57 15 of 16

Author Contributions: The performing data analysis, providing required materials, ideas, formulation of overarching research aims, editing of the text, and data/evidence collection have been performed by K.A.R. and A.T.A. The formulation of overarching research aims, reviewing similar studies, and editing of the text have been performed by S.N.A. Funding: This research received no external funding. Acknowledgments: The authors acknowledge the Ministry of Water Resources in Iraq for collaboration and providing some flow and rainfall data. The authors also acknowledge Mustansiriyah University (www.uomustansiriyah.edu.iq) for the support and encouragement throughout the course of this research. Conflicts of Interest: The authors declare no conflict of interest.

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