Sustainable Development of Wadi Houran- Western Iraqi Desert

rainwater. It is possible to construct small-dam-series of optimal height and location to expand the rainwater harvesting and groundwater recharging. A Current study was done and aimed to establish of oases and natural reserves in order to improve climate conditions, minimize the dust and CO 2 , mitigation of summer high temperature and decrease the soil erosion due to torrents. This study recommended constructing 13 optimal height dams that store about 303 Mm 3 of water, and increase the water surface area of reservoirs in this valley from 15 to 90 km 2 which leads increase the water volume that is recharging ground water from 4.7 Mm 3 to 28 Mm 3 per year.


Introduction
Water scarcity is a global problem caused by the climatic change, the policy neighboring countries and the policy and plans of the country with/of managing water resources. Iraq is one of the Middle East countries that is experiencing water crisis due to the expansion in water project implementations in Turkey and Syria especially with the absence of a bilateral agreement upon water shares distribution of international rivers [1].
Effective planning and management of water resources is necessary to provide fresh water and improve the quality of life especially in arid and semi-arid areas such as Iraqi Western Desert since rainfall is extremely limited and spatially distributed with poorly available groundwater supply [2]. The western desert contains valleys that receive large quantities of torrents water such as Houran, Al-Ghadaf, Tabl ....etc. [3]. Also, they contain several small dams constructed during the 1970s and 1980s with different heights and storage capacities [4]. There are twelve small dams constructed in western desert [5]. Wadi Houran is discharging huge water quantities as surface runoff during rainy seasons and it has only four small dams as shown in Table  (1) and Figure (1). Therefore , many studies were published to cover this important natural phenomena aiming to save as much rainwater as possible.
[6] suggested appropriate sites for water harvesting in Wadi Houran by using (GIS) and Multi Criteria Evaluation (MCE) as a tool for decision support. The results served to organize the subsequent field surveys thus considerably reduce the time and cost of the survey. [7] studied the rainwater harvesting of Houran valley by using remote sensing techniques. Digital Elevation Model (DEM) was applied to determine the suitable sites of small dams, where small lakes along Wadi Horan will lead to increase the agriculture and develop artificial forests to decrease the desertification phenomenon. [8] studied the ability to predict the best water harvesting sites in Houran valley using Model Builder in Arc GIS10.2, which combines various biophysical factors are the slope, runoff depth, land use, soil texture, and stream order. While [9] used Analytical Hierarchy Process (AHP) and pairwise comparison method to predict the best harvesting locations. [10] developed the (Optimal Height And Location Model (OHALM)) and combining it with DEM to design small dam series with optimal heights and locations in this valley.

General Description
Wadi Houran is extending for 458 km from the Iraqi-Saudi borders to Euphrates river south of Haditha city as shown in Figure (2). The geographical location of the valley is between the longitude 39˚00'' 00' to 43˚00''00' East and the latitude 32˚00''00' to 43˚30'00'' North [11]. The valley catchment area is around 13,370 km 2 and the difference in elevation from the beginning to the end is around 600 m. Wadi Houran region is classified as an arid region characterized with hot summer and cold winter [8]. The average annual rainfall is 115 mm. The annual average of relative humidity ranges between (19%-82%) which varies largely from month to another during the year. Wadi Houran is characterized by considerable temperature ranges between (0-48) • C [6].
The annual evaporation value for the study area ranges between (1600-1900) mm as shown in Figure (3). The highest evaporation value occurs in July and August [12].

Geological Description
The whole course of Wadi Houran is located in the Western Desert

Biological Description
There are many oases in Wadi Houran.

Future goals for developing the study area
This research focuses on developing the study area by achieving the following goals:

Environment and ecology improvements:
a. Harvesting rainwater by constructing small-dam-series leads to improve the climate, increase the recharge of groundwater, and improve its quality. About 90 km 2 of water surface area of reservoirs behinds 4 dams and 13 proposed additional small dams. Bird and fish with trees surrounding reservoirs will create a very healthful environment.
b. Planting forests around reservoirs and shallow wells using renewable energy pumps will create good environment habitations to the plants and animals that live in the desert conditions. c. Establishing renewable energy stations due to the presence of sufficient sunny hours in general, and high wind speed in areas with a height more than 700 m above sea level around Rutbah city.

Security aspects:
a. Creating job opportunities in agricultural and pastoral sectors, without violating the valley environment.
b. Planning to increase the population density per unit area within the region's ecosystem.

Data Source:
The results of the present study based on different types of data, which was collected from different sources to identify the optimal height and location of small dams:

Fig. 12 Flooding in study area (25/11/2018)[21]
It is very difficult to predict the rainfall-runoff relation in western desert of Iraq because of the lack of hydrological data.
Land cover, land use and soil properties lead to predicting runoff by using hydrological models. So the Watershed Modeling System (WMS) is used to estimate the runoff using remote sensing data. Multiple steps are required to produce the necessary layers in WMS Tools [22]. Wadi Houran has the largest value of surface runoff and water harvesting volumes among other valleys in western desert as shown in Table 3.

Groundwater Recharging:
As the sediment loads was disposed in the reservoirs behind small dams, the fine particles will decrease the hydraulic conductivity of the soil in the reservoir bed. The conductivity will decrease and approach to the

Water Harvesting:
Wadi Houran is discharging huge amount of rainwater runoff which reaches billion m 3 during some observed years

An Optimal Height And Location Model (OHALM) was developed by
[10] to propose the optimal dams series in Houran valley. Table 4 and Figure 7 illustrated 13 small dams that their total reservoir volume is 303.2 million m 3 . If these dams were constructed, the total harvested volume of all 17 dams is 350 million m 3, which is less than the average surface runoff volume recommended by [16].
Many weather stations must be constructed in this valley in order to observe rainfall and surface runoff date. This study recommends constructing these 13 dams and improves the hydrologic information by updating observation of sufficient weather stations in order to study the economic feasibility of constructing other dams.

Groundwater Recharging:
One of the objectives of constructing a small dam in western desert is to recharge the groundwater and sustain the water resources. The minimum possible recharging quantities can be estimated by considering only the reservoir recharging after decreasing its bed hydraulic conductivity due to the sedimentation of fine particles. Constructing proposed 13 small dams will increase the reservoir area close to 90 km 2 . The water infiltrated volume through this area when assuming the minimum hydraulic conductivity of 31.54 cm/year is about 28 million m 3 .

The best location of a natural reserve for wild animals:
Target area of 4000 km 2 is selected in the midstream of the valley, fig. (13) explains this area which shown as green polygon.
There are many constraints affecting the best location to construct the natural reserve.

5-Renewable energy aspects.
For 1 st constraint, it is clear that both the east and west ends of target area is the best soils to harvest more rainfall water, but the east end is far from the main road, (Figure 13), and the groundwater in this region is very salt, (fig. 14). The west end of target area is better for the nature reserve; it is plotted as a yellow rectangle near Rutbah city as shown in Figure (14). Although the 2 nd constraint don't verify the same location because the groundwater depth is decreased as the distance to Euphrates river is decreased, but 3 rd constraint is more active because the salinity in east zone is greater than 10,000 ppm, so it isn't suitable only to irrigate high tolerance crops. Water quality is better in the west of the target area, the water quality in yellow rectangular is about 1000-1500 ppm. It is potable water so it is suitable to any sensitive plants and livestock.
It is very important to expand water-harvesting technique and construct the best ranking small dams that closer to this area in order to sustain the groundwater quantity and quality by recharging the aquifers.
4 th constraint also verify the selected location, the distance from the main road is about 3 km only as shown in Figure (13).
For the potential renewable energy constraint, There's no variation in sunny hours among the valley's locations, but the best location for high wind speed is nearly to Rutbah city. So the yellow rectangle is verifying this constraint.
The current study recommends selecting the location that verify these active constraints.
The yellow rectangular in fig. 14

3-Third stage (2031-2050):
a-Complete the proposed small dams series of 13 dams by constructing the last 7 among the valley and surrounding all reservoirs by forests.
b-Expanding the reserves that constructed early.
c-Monitoring water quantity and quality in aquifers and study the system sustainability.

Conclusions and Recommendations
According to the scarcity of hydrological data about Houran valley due to the existence of only one weather station covering the large area (18,000 km 2 ), it is very difficult to predict the surface runoff quantities. therefore, it is very important to establish at least 8 stations. Establishing a natural reserve and planting forests is really important to invest this valley's large area with huge surface runoff quantities to improve the ecology system and climate conditions. About 400 million m 3 of harvested high quality water can be used to irrigate millions of several types of trees which are reducing dust, erosion, CO2 and improving the environment and ecology system.
Small dam series of 13 optimal height and location dams leads to increase the free water area in the valley from 15 to 90 km 2 which will lead to improve the climate conditions and ecology of the valley. Recharging ground water by 31.54 cm/year means feeding the valley aquifers by 28 million m 3 /year instead of direct rainwater feeding. These large recharging quantities will sustain the water resource quantity and quality in the oases and reserved regions.
Upper Euphrates Basin Developing Center-University of Anbar is planning to establish an active weather station network and study the rainfall, runoff, infiltration, groundwater aquifer types and its well networks, annually average recharging and safe yield.