Water balance of the basin of Mandali / east part of Iraq

Mandali Basin is located between latitudes (33◦ 39' 00" and 33◦54' 55") to the north and longitudes (45ο 11' 00" and 45ο 40' 00") to theeast; to the east of Diyala province at the Iraqi-Iranian border; thebasin area is approximately 491 km2.From the study of climate reality of the basin between 1990-2013and assessment of the basic climate transactions, it was foundthat the annual rate of rainfall is 253.02 mm, the relative humidity(44.4%), the temperature (21.3 ◦C), wind speed (2.08 m /sec.),sunshine (8.27 h/day) and evaporation of the basin class (a) (271.98mm) and corrected potential evapotranspiration (80.03 mm). Theresults of the data analysis show that, there are three basic periods ofclimate variability wet period, semi wet and dry period.This study shows that, there is water surplus of 60.87% of therainfall amount which is equivalent to 154.03 mm, the amount ofrunoff is 7.47 mm, and the amount of water recharge is 146.56mm.


Introduction
Mandali Basin is located between latitudes (33 • 54 " 55 ' -33 • 39 " 00') to the north and longitudes (45 • 40 ″ 00′ -45 • 11 ″ 00 ′ ) to the east; to the east of Diyala province, at the Iraqi-Iranian border; the basin area is approximately (491 km 2 ). Fig.1 it can be seen that, the rock exposures in the basin extends from the age (Pliocene-Recent) which is represented by Euphrates, Fetha (lower Fars), Anjana (upper Fars) and Muqdadiyah and Bai Hassan as well as the deposits of Quaternary [1].

Study area
Structurally the study area is located within the central eastern part of the Mesopotamian plain and at the southwestern part of the foothill [1]. Region containing some of the geomorphological phenomena of the basin, which is the hills, plains and valleys, as, characterized by the presence of the parallel and dendritic drainage patterns [2]. The area is represented as a good agricultural land where pomegranate orchards and palm are present with cultivation of seasonal crops, wheat and barley. Also famous for herding sheep and cows are a better area in Iraq.
The study of climatic elements in hydrogeological studies is aimed to calculate the water balance of the groundwater. One of the climate factors which affects the calculating is that the amount and intensity of rainfall, the spread of the fallen and the relative humidity, which is considered as one of the water availability elements in the region. While the temperature, sunshine, wind speed and evaporation of the basin class (a) and the potential evapotranspiration basic elements of water loss. Atlas has to take advantage of Iraq's climate and climate information recorded in the stations Badra (Ba) and Khanaqin (Ka) for the period (1990-2013) and through the monthly averages of climate elements account for the Mandali.  Due to the occurrence of Mandali basin between stations Badra climate and Khanaqin, the arithmetic mean is used to extract the monthly values of different climatic elements of the proposed station Mandali Table 2.

Water surplus (WS) and water deficit (WD)
Water surplus is defined as the excess of rainfall over the corrected potential evapotranspiration values during specific months of the year, while water deficit is the excess of corrected potential evapotranspiration values over rainfall during the remaining months of that year. According to [5], the actual evapotranspiration APE can be derived as follows: APE = PEc when P ≥ PEc APE = P when P <PEc In the first case (water surplus period) the value of rainfall is greater than PEc, and the APE is equal to the PEc value; while in the second case (water deficit period) PEc is greater than rainfall; the APE is equal to rainfall values as expressed in the following: WS = P -PEc P >PEc, PEc = APE WD = PEc -P P <PEc, P = APE where: WS: Water surplus (mm) WD: Water deficit (mm), P: Rainfall (mm), PEc: Corrected potential Evapotranspiration factor (mm). APE: Actual Potential Evapotranspiration factor (mm).
The WS and WD are calculated without using the soil moisture (equal to zero). Table 4 shows the monthly averages of APE, WS and WD; the water surplus period is limited between November and March because rainfall exceeds PEc, while the remaining months represent water deficit period where PEc exceeds the rainfall.

Pec (mm)
The WS amount is (153.034 mm) from total rainfall (253.02 mm), therefore the water surplus ratio from the annual rainfall can be represented as: WS % = WS / P × 100 WS % = 153.034 / 253.02 × 100 = 60.87 % This percentage represents the groundwater recharge and surface runoff. While the amount of WD is (860.59mm) from the corrected potential Evapotranspiration (PEc), which equal to 39.13% from the total rainfall as in the following equation: WD % = 100 -WS % WD % = 100 -60.87 % = 39.13 % Fig. 2 shows the relationship between the monthly average of rainfall and corrected potential evapotranspiration, which shows the water surplus and water deficit periods.
Surface Runoff is an important component of the water balance of the hydrological basins. The annual runoff verified account of the water surplus in the study area by adopting the following mathematical formula [6]. R s = (P -17.8) P / 254 Ws = R s + R e Where: P: Total annual rainfall (mm) R s : surface Runoff (mm) R e : Groundwater Recharge (mm)

WD
The limitations of the applied this equation to calculate the runoff basins hydrological is that the total annual rainfall is not less than 178 mm. The water balance calculations is performed by depending on the rainfall and the potential evapotranspiration rates for the period (1990-2013) set out in the Table 4 where the total annual rainfall was 253.02 mm with water surplus (154.034) mm, which is constitute a percentage of annual rainfall (60.87%) mm. This increase is divided into the surface runoff (Rs) value of (7.47) mm, the rate of annual rainfall (2.95%), and the groundwater recharge (Re) value (146.56 mm) and the rate of annual rainfall (57.92%). In general, the rate of water surplus generated from the annual rainfall was 60.87% offset 39.13% water loss through actual evapotranspiration.

Climate classification
The average of the monthly rainfall values and temperature is used to determine the climate detailed basin Mandali according to the type of classification [7,8] who adopted the Humidity Index (HI), which represents the ratio between the rainfalls (P) to the potential evapotranspiration (PE).
According to the application of both classifications, which are mentioned above, the predominant type of climate during the months of the year of the study area as shown in the Table 5. H.I. = P/PE The climate class is identifying by using the annual dry coefficient, which is suggested by Al-Kubaisi [9]. This classification, which depends on the rainfall and temperature, shows that the climate of the study area is a Sub arid. 2. This study showed that there is the water balance in the basin by 60.8% of the amount of rainfall, which is equivalent to 154.034 mm. 3. The water balance is divided into surface runoff 7.47 mm with a rate of 2.95% and groundwater recharge of 146.56 mm with a rate of 57.92% of the annual rainfall. The water deficit represents 860.59 mm of the corrected potential evapotranspiration. 4. This study showed that the climate of the study area is between the wet climates in winter to the dry climate in summer and in general, it can be considered that the climate of the region is Sub arid.