EVALUATION OF SUITABILITY OF DRAINAGE WATER OF AL-HUSSAINIA SECTOR (KUT IRAQ) TO IRRIGATE COTTON CROP

In this study, a specified area of Al-Hussainia sector (which is the middle sector of Al-Dalmaj irrigation project in Kut city/ Iraq) has been selected to be evaluated for its water suitability to irrigate cotton plant. The evaluation include: first Chemical evaluation of drainage water, second Analysis of drainage water by Aq.Qa software, and third computations of Leaching requirements for cotton crop. For the chemical evaluation the most important indicators for the salinity problem considered are (Electrical Conductivity, Total Dissolved Solids, Sodium Adsorption Ratio (SAR) and Sodium Content). The analysis of the hydrochemical results by Aq.Qa program shows that the internal consistency of the samples was acceptable. It is concluded that in the months July to October most of the measured concentrations of the tested elements were greater than the other four months because in hot weather the evaporation will increase which decrease the quantity of dissolved oxygen in water which cause the increase in concentrations of these elements. However the drainage water of Al-Hussainia sector can be used directly to irrigate cotton without reducing the yield with leaching requirement of 0.18 for location 1, leaching fraction of 0.17 needed for locations 2 and 6, while a leaching fraction of 0.16 should be provided for locations 3 ,4 ,and 5. However there is no need to mix the drainage water with fresh water.

It is concluded that in the months July to October most of the measured concentrations of the tested elements were greater than the other four months because in hot weather the evaporation will increase which decrease the quantity of dissolved oxygen in water which cause the increase in concentrations of these elements. However the drainage water of Al-Hussainia sector can be used directly to irrigate cotton without reducing the yield with leaching requirement of 0.18 for location 1, leaching fraction of 0.17 needed for locations 2 and 6, while a leaching fraction of 0.16 should be provided for locations 3 ,4 ,and 5. However there is no need to mix the drainage water with fresh water.

INTRODUCTION
Water is an essential and basic human need for urban, industrial and agricultural use and has to be considered as a limited resource. In this sense, only 2.5% of the total water resources in the world can be considered as fresh water, in 2025 nearly one-third of the population of developing countries, some 2.7 billion peoples, will live in regions of severe water scarcity. In dry areas where water is scarce it is very important to exploit all available water. The use of drainage water is an important strategy for supplementing water resources. Also reuse helps to avoid environmental problems such as water pollution. Furthermore, reuse may help alleviate drainage disposal problems by reducing the volume of drainage water involved [11].
Many researches have been done around the world about the reuse of waters of marginal quality. Drainage water is one of these waters and can be reused successfully to irrigate some crops [11].
A project evaluation is a step-by-step process of collecting, recording and organizing information about project results, including short-term outputs (immediate results of activities) and longer-term project outcomes (changes in behavior, practice or policy resulting from the project). Project evaluation is used to conduct a systematic and comprehensive assessment of the relevance, performance and impact of the project in the context of its stated objectives. This means, it reviews the relevance of the project to solve the identified problems. It also makes analysis of the project inputs, activities and results and compares these with the designed bases.
The results are used to adjust the planning or implementation strategy to ensure the required project results [7].
The aim of this study is to evaluate the suitability of drainage water to irrigate cotton crop. The case study was a specific area of Al-Dalmaj project/Al-hussainia sector (kut/Iraq). The evaluation program involves the effect of salinity on cotton crop production, computing the leaching requirements and finding what if there is need to mix drainage water with fresh water.

PROJECT DESCRIPTION
The study was conducted in Al-Dalmaj project/ Al-hussainia sector (in Kut city/ Iraq). It is located between 45• 28' to 45• 45' eastern longitude and 32• 28' to 32• 10' northern latitude. The project area covers 59 382 hectares (237528 donums) and extends about 33.3 km from north to south and 28.3 km from west to east, at its broadest. Al-Hussainia sector was constructed in 1974 and it is located between 45• 39' to 45• 45' eastern longitude and 32• 28' to 32• 10' northern latitude. The project area covers 25237.25 ha (100949 donums) with total length of 34.2 km and extends about 29 km from north to south and 12.5 km from west to east, at its broadest. The area Al-Hussainia sector serving is bounded from the west by Al-Hussainia main canal, and by Al-mazzaq main canal from the east. Ground elevations in the area vary between 16.15 t`o11.45. Fig. 1 shows the site plan of Al-Dalmaj project [1].

METHODS OF USING DRAINAGE WATER
Two methods will be discussed for utilizing Al-Hussainia main drain's saline water to irrigate the cotton crop these methods are cyclic and blending.

Cyclic
Saline drainage water is used solely for certain crops and only during certain portions of their growing season. The objective of the cyclic method is to minimize soil salinity during saltsensitive growth stages, or when salt-sensitive crops are grown. With a cyclic method, the soil salinity profile is purposefully reduced by irrigation with good quality water, Thereby facilitating germination and permitting crops with lesser tolerances to be included in the rotation. The cyclic method keeps the average soil salinity lower than that under the blending method, especially in the upper portion of the profile, which is critical for emergence and plant establishment [6].
Drainage water can be used to irrigate crops directly using cyclic method, but the accumulation of excess soluble salts in the root zone is a widespread problem that seriously affects crop productivity. To prevent the accumulation of excessive soluble salts in irrigated soils, more water than required to meet the evapotranspiration needs of the crops must pass through the rootzone to leach excessive soluble salts. This additional irrigation water has typically been expressed as the leaching requirement (LR). To estimate the leaching requirement, both the irrigation water salinity (ECw) and the crop tolerance to soil salinity (ECe) must be known [14].
The necessary leaching requirement (LR) can be estimated from Fig. 2 for general crop rotations.

Fig. 2. Effect of applied water salinity (ECw) upon root zone soil salinity (ECe) at various leaching fractions (LF) for 100% yield potential [5]
For more exact estimates for a particular crop, the leaching requirement equation (Eq. 1) should be used:

ECe Soil Electrical Conductivity
In many texts, the Terms 'leaching fraction (LF)' and 'leaching requirement (LR)' are used interchangeably. They both refer to that portion of the irrigation which should pass through the root zone to control salts at a specific level. While LF indicates that the value be expressed as a fraction, LR can be expressed either as a fraction or percentage of irrigation water. In this study we used the term "leaching requirement" [12].

Blending
Blending involves mixing saline water and good quality water together to achieve an irrigation water of suitable quality based on the salt tolerance of the chosen crop. Blending is not attractive if saline water does not supply at least 25 percent of the total irrigation water requirement. That is, the costs and risks of the increased management associated with adding salts to the irrigation supply will likely outweigh the benefits from increasing the total water supply by only a slight to modest amount [6].
If there were two water resources the first one is (a) and the second is (b), the quality of the blended water can be found by using equation (2): Where the concentration can be expressed as either ECw or ppm but the same units of concentration must be used throughout the equation [5].
The mixing ratio can be found by equation (3): In this research the closest fresh water resource to the main drain is Al-Mazzaq cannel. Al-Mazzaq cannel chemical analysis results are typed in Table 1 and these results were taken from water department laboratory.

THE CHEMICAL EVALUATION
The criteria used to evaluate the quality of drainage water for use in agriculture are salinity of irrigation water for salt built up in soils and its adverse effect on plant growth, sodicity for its deleterious effect on soil physical properties, Residual Sodium Carbonate(RSC) for its effect on final soil water SAR value with the loss or gain in Ca and Mg concentrations due to the precipitation or dissolution of alkaline earth carbonate, and Toxic Effects of specific Ions in irrigation water such as Na ,Cl ,SO4 and B on plant growth and yield [4].
Besides the above indicators, a mathematical equations and models were applied to evaluate the water quality for its reuse in irrigation in Al-Hussainia sector these equations are: Sodium Adsorption Ratio is defined by [13]: The Residual Sodium Carbonate equation is [13]:

RSC = (CO3-2 + HCO3-) -(Ca +2 +Mg+2) 5
All concentrations are expressed in (mg/l) [13]. Table 2 shows the classification of irrigation water according to SAR. , Table 3 shows the classification of irrigation water according to Residual Sodium Carbonate.  [9] Level SAR Hazard S1 <10 No harmful effects from sodium. S2 ≥10-<18 Appreciable sodium hazard in fine-textured soils but could be used on sandy soils with good permeability. S3 ≥18-<26 Harmful effects could be anticipated in most soils and amendments such as gypsum would be necessary to exchange sodium ions. S4 ≥26 Generally unsatisfactory for irrigation. High salts can reduce or even prohibit crops production and can reduce water infiltration which indirectly affects the crops. An understanding of the quality of water used for irrigation and its potential negative impacts on crop growth is essential to avoid salinity problems. Water quality and soil chemical analyses are necessary to determine which type of salts are present and the concentrations of these salts [10].
For the chemical evaluation, six samples were taken from six locations of Al-Hussainia main drain (from july 2012 to February 2013). Locations of the samples are marked by the green points as shown in Fig. 3.

Chemical evaluation
The results of chemical analysis of drainage water of Al-Hussainia main drain are shown in Table 4. From these results it can be concluded that there is a salinity problem especially during summer months where the concentrations are much higher than the limited values, while there is no soudicity problem.
In the months July to October, most of the measured concentrations of the tested elements were greater than the other four months because the hot weather will increase the evaporation which decrease the quantity of dissolved oxygen in water which cause the increase in concentrations of these elements.
Water analysis of the results by Aq.Qa software showed that: 1-The internal consistency (e.g. Anion-Cation Balance) of the samples was within the limits.
2-The Residual Sodium Carbonate (RSC) was zero because the bicarbonate concentrations were low.
3-There was high salinity hazard while there was no sodium hazard.
4-The program determined the water type (e.g., Ca-HCO3 or Na-SO4) by finding the predominant inorganic cation and anion. The water type was figured on the basis of electrical equivalents (Aq.Qa user's guide). In this study, the predominant inorganic cation was Ca +2 and the predominant inorganic anion was at most Cland sometimes SO4.
5-This program also indicate magnesium hazard in all locations in October ,in location 4,5,6 in September and 5,6 in February while there is no magnesium hazard in the other months . For the likelihood prediction of soil water salinity, sodicity and toxicity related problems resulting from irrigation, we can use the method that is presented by Rhoades, et.al, (1992). With this procedure salinity, or solute concentration, is estimated by multiplying the EC (or solute concentration) of the irrigation water by a relative concentration factor, Cf, appropriate to the leaching fraction and depth in the rootzone. These factors are given in Table 7.The assessment of water for irrigation suitability is made based on tolerance of the crop to the predicted levels of salinity (EC), sodicity (SAR) and concentration of toxic ions.
In the following section, this method was applied to drainage water of Al-Dalmaj project/Al-Hussainia sector to assess its suitability for irrigation. The results are plotted in Figs. 5-8. Let's take Fig. 5 for example: in location 1 the leaching requirements of 0.05 and 0.1 are unsuitable for direct irrigation because the salinity will rise above threshold value for cotton crop and so on for the chloride and boron concentrations.
From Fig. 8 it can be conclude that there was no sodicity hazard where all values situated on area of unlikely permeability hazard.   2. The drainage water can be used safely to irrigate cotton crop directly without reducing the yield (100 % yield potential) providing leaching fraction of 0.18 for location 1, leaching fraction of 0.17 is needed for locations 2 and 6, while a leaching fraction of 0.16 should be provided for locations 3, 4, and 5.