حسن هادي مهدي العريّض

Drought is a natural disaster associated with a shortage of water availability for specified region within a specific time period. The impacts of drought are significant and extend to damage many important life aspects such as environmental, economic, and social activities. The forecasting of the drought events is an essential element for planning this disaster, reducing its effectiveness and response. The three characteristic frequency, intensity, and time period are the key parts for forecasting and assessment of droughts. Here, two drought indices (The Reconnaissance Drought Index (RDI), standardized precipitation index (SPI)) were used for forecasting of the future drought within Al Najaf city, Iraq. Thirty years meteorological data (average monthly precipitation and temperature) were used for the period (2021–2050) downloaded from the site of the Centre for Environmental Data Analysis (CEDA) for five grid points to cover overall study area. The computation of these indices conducted at a 12-month time scale and included the calculation of potential evapotranspiration by Thorthwaite method. The temporal drought intensity as well as drought frequency configurations were calculated and analyzed for each drought index. The results showed that the general average drought level expected will mildly dry while the maximum drought level expected will extremely dry. The more severe seasons of drought were forecasted in the years 2038, 2034 and 2021, respectively. Also, the prevailing event will be a one year drought and the maximum drought interval occurred within the study period will four consecutive years, with a 3.33% exceedance probability.

In the field of water resource management, rainfall intensity-durationfrequency (IDF) curves are of great importance, especially in the design of hydraulic structures and the assessment of flash-flood risks. The aim of this study is to obtain IDF curves and find empirical equations for rain duration for Al-Najaf city in the southwest of Iraq. Rainfall data for 30 years, from 1989 to 2018,were collected. The practical reduction equation of the Indian Meteorological Department (IMD), with six methods of probability distribution, was used for short intervals (0.25, 0.5, 1, 2, 3, 6, 12, and 24 hours) with a specified recurrence period (100, 50, 25, 10, 5, and 2 years). The Kolmogorov-Smirnov, chi-squared, and Anderson-Darling goodness of fit tests were used with the help of EasyFit 5.6 software. The findings revealed that the highest intensity of rainfall occurs during a repeated cycle of 100 years with a duration of 0.25 hours, while the lowest intensity of rainfall occurs during arepeated cycle of 2 years with a duration of 24 hours. In the results obtained fromthe six methods, as well as the superiority of the log Pearson type III method, the consistency of the fit tests showed some convergence.

A 3D groundwater steady-state flow conceptual model was built for all of Iraq using a MODFLOW package integrated with the Groundwater Modeling System to simulate the groundwater movement and flow direction for the upper zone of Iraq as well as to compute the water budget for all aquifer systems in Iraq. This model was run for seven scenarios of climate change conditions for the period of 2020-2050. A Representative Concentration Pathway model (RCP4.5) was used for the prediction of future rainfall over the next 31 years. The results showed that the decline in rainfall will be 6.247% due to climate change impacts. The decline in rainfall will cover two-thirds of the area of Iraq. Seven scenarios simulating groundwater flow behavior showed that decreased soil moisture content will significantly reduce groundwater recharge and increase runoff. A decline in groundwater levels by an average of 1.8-4.8 m will occur for the upper zone of Iraqi aquifers over the next 31 years. These results will help Iraqi decision-makers improve water resource management.

Groundwater recharge in arid and semi-arid areas such as Iraq considered one of the most significant factors affecting the groundwater aquifer systems behavior. Due to lack of direct measurements of recharge or carrying out of very detailed field studies (difficult activities), it is an important role for spatial variables in estimation of recharge. The fluctuation of groundwater is controlled by many factors. It influenced spatially and temporally by the climate change, soil characteristics, geology, land cover, slope and the depth of groundwater level. Many ways used for calculate or estimate groundwater recharge, selected of the suitable method depending on the state of the study area, financial, required accuracy, and available time. In this study, two dimensional geo-statistics interpolation methods (inverse distance weighted(IDW) and Kriging ) integrated within two dimensional scatter points module in GMS software were used in order to determine the groundwater distribution over all Iraqi catchment area. The Calculated groundwater recharge data which used in this models, was obtained from the balance equation which was conducted for all Iraqi governorates .The balance equation was depended on parameters of rainfall, temperature, evaporation, surplus, and SCS runoff. The results showed that the best method for predicted groundwater recharge was Kriging method with coefficient of determination (R2 ) equals to 88.80% and with less values of root mean square error (RMSE), mean bias error (MBE), and mean absolute error (MAE) which equals to 19.65, 79.59, and 14.36, respectively. Also, the results of groundwater recharges were converted to contour lines which its values will help the other researchers in hydrology, hydrogeological and water resources engineering for any study about the groundwater flow and transport of the contaminant.

Estimating of soil hydraulic conductivity was so important and essential parameter for designing systems. Hydraulic conductivity measurements need many activities beginning from extract samples. Therefore it is having been found costly and time-consuming. At the present time, geo-statistical ways were used to estimate the hydraulic conductivity on the basis of restricted data. The aim of this research is to characterize hydraulic conductivity for the upper zone of Iraqi aquifers using groundwater modelling system (GMS) software and to build two dimensions geo-statistical analysis model depending on the application of 868 wells.These wells were divided into 778 wells for building the model and 90 wells for the verification. The hydraulic conductivity parameter which was obtained from the geo-statistical analysis model results indicated that the best fitted theoretical model was the inverse distance weighted (IDW) model with a coefficient of determination (R2 ) equal to 87.43% and root mean square error (RMSE) equal to 1.853. Also, by conducting many trails, it was found that the optimal distance range for estimating the hydraulic conductivity was 3800 to 5000 meters. A comparison between the kriging and IDW interpolation methods indicated that

Gravity Dams depend mainly on its own mass to resist the effecting uplift pressure. The effect of uplift pressure can be reduced by using a drainage gallery. The optimum position of the drainage gallery under gravity dam results maximum drain reduction factor. in this study, numerical method (two dimensional finite element) are used to analyze hydraulics of uplift pressure under the gravity dam and its effect on usage of gallery drain, and without gallery drain for different reservoir and drain location along the base of the dam. Two models used once without sheet pile and another with sheet pile. drain reduction factor (DRF) had been calculated to demonstrate the effect of used gallery drain in the system. the results indicate that the gallery drain nearest the upstream side close to Xd/B=0.167 results in maximum (DRF) close to 0.494, and can be achieved as the optimum position of the drainage gallery, at which seepage discharge entering the drainage gallery is maximum. The results of comparison between the two models showed that the usage of gallery drain and sheet pile in the system reduces the uplift force more than 40% and 20% respectively. The analysis process depends on computer program package "SLIDE V.5.005".