حيدر فاضل عذاب الزبيدي

Subsurface tile drains in areas with intensive agriculture can be a major contributor of salinity loadings to streams and rivers, as salts in soil and groundwater are transported into the tile drains. Modeling tools can be used to assess baseline conditions, quantify salt mass export, and assess management scenarios to decrease salt removal. In this study, a newly developed version of the SWAT model for salinity transport, SWAT-Salt, was modified to include salt ion transport in subsurface tile drains and used to explore the effects of region-wide implementation of subsurface drainage on salinity transport and export from an irrigated semi-arid watershed. The model includes the transport of 8 major salt ions (SO4, Ca, Na, Cl, Mg, K, CO3, HCO3), and with the inclusion of tile drain transport simulates the fate and reactive transport of these ions in soil water, groundwater, tile drain water, and stream water. The SWAT-Salt model is applied to a 732 km2 salinity-impaired irrigation region within the Arkansas River Valley in southeastern Colorado. The model is first tested against salt ion data in effluent from a 15 km2 tile drainage district, and then applied to the entire region to assess the impact of region-wide implementation of subsurface tile drainage on in-stream salt ion concentrations, in-stream salt ion loading, and total salt export from the watershed. The model can be a useful tool in simulating salinity transport in tile drained watershed and investigating the effect of salinity management practices at a variety of spatial and temporal scales.

The afflux in hydraulic engineering is the maximum change of the water surface upstream of the hydraulic structure. Afflux is an important consideration to satisfy the design of the bridge. This study statistically analyzes the afflux amount. It was applied to lab experiment data which were useful for the dimensional analysis technique. As a result of the model, it has been found that the Froude number has the most significant effect on the afflux amount in the model. The contraction ratio and the angle of pier axes normal to the flow direction respectively have less effect on the afflux amount. Pearson correlation coefficient is found to be equal to +0.94 which indicates a strong positive correlation between observation and prediction values. The mean absolute error (MAE), mean square error (MSE), and root mean square error (RMSE) were calculated which were 0.008, 0.0001, and 0.011, respectively. All these values were close to zero, this indicates that the equation gave results of agreement for the forecast afflux. Also, the value of NSE was computed equal to 0.89, which was the closest to 1, which indicates that the equation was of an acceptable level performance. The coefficient of determination was found to be equal to 0.98 which also reflects a better fit for the model. Keywords: Afflux, Contraction ratio, Froude number, Oblong pier

This paper presents an analysis of the annual precipitation observed by a network of 30 rain gauges in Iraq over a 65-year period (1941–2005). The simulated precipitation from 18 climate models in the CMIP5 project is investigated over the same area and time window. The Mann–Kendall test is used to assess the strength and the significance of the trends (if any) in both the simulations and the observations. Several exploratory techniques are used to identify the similarity (or disagreement) in the probability distributions that are fitted to both datasets. While the results show that large biases exist in the projected rainfall data compared with the observation, a clear agreement is also observed between the observed and modelled annual precipitation time series with respect to the direction of the trends of annual precipitation over the period.

In this research, the sediments' transport and how to compute their amount have been studied in Al-Meshkab regulator channel. Twenty four cross-sections were selected along the reach of Euphrates river to study the characteristics and the rate of transport of sediments. The measured data included: cross-sections of the channel, average velocity, discharge, water surface width, water surface slope, sediment concentration, bed material samples as well as the specific gravity of bed sediments. The length of the study region was 6 km upstream of Al-Meshkab regulator. The study was divided into two parts: the practical part (field and laboratory works) and the statistical part. The research covered the suggestion of an empirical formula which was used to fit the dimensionless form and to predict a relationship between the sediment rate and the different variables. Analysis of Variance (ANOVA) was used to examine the differences between the observed sediment rate and the predicted sediment rate. Results indicated that no statistically significant differences could be detected between observed and computed sediment rate values using the statistical model.

Groundwater and drainage-water sustainability is crucial to water management. Controlling the interaction between the groundwater and drain-water salinity at the watershed level has only been the topic of a limited number of studies. This study statistically compares salt concentration rate across time and four different flow regimes. We sampled water from 2014 to 2018. The study used R software to analyze water-quality parameters utilizing PCA and indices. Multiple water-quality indices were used to test irrigation water. A linear model with TDS as the response was fitted to the data. Another two-factor repeated-measurement covariate model was built. Water-quality indices suggest that measured water from varied flow regimes in the study area is suitable for irrigation. Based on the statistical models, Tukey's adjustment pairwise demonstrates considerable salinity variations between drain water and surface water. However, the main effect of the flow regime on TDS is significant. This indicates that the TDS value varies depending on the flow regime, not on time plus the interactions between these regimes

Civil and Environmental Engineering Civil Engineering Addab, Haider Fadhil Adviser(s): Ryan Bailey Dissertation: Salt Transport and Loading in Tile-Drained Watersheds: Observations, Modeling, and Management