The basic reason behind the need to monitor water quality is to verify whether the examined water quality is suitable for intended usage or not. This study is conducted on Al Shamiya al sharqi drain in Diwaniya city in Iraq to make valid assessment for the level of parameters measured and to realize their effects on irrigation. In order to assess the drainage water quality for irrigation purposes with a high accuracy, the Irrigation Water Quality Index (IWQI) will be examined and upgraded (integrated with GIS) to make a classification for drainage water. For this purpose, ten samples of drainage water were taken from different ten location of the stuay area. The collected samples were analyzed chemically for different elements which affect water quality for irrigation.These elements are. Calcium(Ca+2), Sodium(Na+), Magnesium(Mg+2), Chloride, Potassium(K+), Bicarbonate(HCO3), Nitrate(NO3), Sulfate, Phosphate, Electrical Conductivity(EC), Total Dissolved Solids (TDS), Total Suspended Solids (TSS) and pH-values (PH). Sodium Adsorption Ratio (SAR) and Sodium Content (Na%) have been also calculated. Results suggest that, the use of GIS and Water Quality Index (WQI) methods could provide an extremely interesting as well as efficient tool to water resource management. The results analysis of (IWQI) maps confirms that: 52% of the drainage water in study area falls within the Low restriction (LR) and 47%of study area has water with (Moderate restriction)(MR),While 1% of drainage water in the study area classified as (Sever restriction) (SR). So, the drainage water should be used with the soil having high permeability with some constraints imposed on types of plant for specified tolerance of salts.