Being a country with limited freshwater resources, Yemen facing a water crisis due to rapid depletion of groundwater and the lack of surface water availability. Dhamar governorate, which is located about 100 km from the south of Sana'a (the capital), is one of the arid regions in the country. This research aims to explain the current situation of water resources and to get better planning for water resources management in the governorate. The rainfall is low and have spatial and temporal variation as well as the non-renewable groundwater abstraction is high. Previous studies in Dhamar plain showed that the total inflow and outflow were approximately 659.36 and 771.51 MCM/year respectively, which gives negative change in storage of about 112.15 MCM/year. Groundwater table declined in the last 40 years at a rate of 2.0 to 2.5 m/year, because of the high abstraction of groundwater from the entire area. It is predicted with the growth rate of 2% in water abstraction, which is normally expected in developing the economy, the shallow groundwater would be exhausted within the next 30 years. In Dhamar plain, it was found that the irrigation supply for irrigated areas of single, double and perennial crops were about 90, 95 and 95% from groundwater while the remaining percentage supplied from surface water. In general, the classification of cultivated area according to the sources of irrigation not only in Dhamar plain but in all the governorate in 2013 was about 27 and 73% from groundwater and surface water respectively, which was changed in 2015 to 39 and 61% respectively. This means that there is a probability stress on groundwater in the future in agriculture sector. Better water resources management and conservation with planning are very important to apply in the governorate to solve the problem of water shortage in the future and conserve the non-renewable water resources. From this study, different scenarios suggested to adopt with the scarce in water resources.

In such problematic water situation in Egypt, control and saving of the available limited quantity takes great importance from both technical and national points of view. In addition to all the well-known traditional reasons of the problem such as pollution, over usage, and bad traditions of dealing with water, a new very important reason is added nowadays, called "Climate Changes" which has a direct impact on sea water rising, that causes a serious attack of the salt water to the fresh water especially in River Deltas., Not only the surface water, but also the ground water. Since that process proved some acceleration, several investigations have recently considered the worst impacts of climate change and sea water level rise on sea water intrusion. Most of them have revealed the severity of such problem, and the significance of the land movement of the dispersion zone under the sea water level rise situation. In this paper, we try to introduce a technical review and study for the most popular studies concerning our topic, and its most important conclusions, as an approach for preparing the Ph.D. thesis about the Nile Delta water equilibrium in the light of the expected Mediterranean Sea water level rise. Nile Delta, which located between Damietta Branch on the East, and Rosetta Branch on the west, occupies about 20000 square kilometers of the most rich, productive land in Egypt. About 50% of Egyptian population live in that area, agriculture is the main human activities on them, so water is the prime factor in their life, and their agriculture investments. The great amount of this investment depends on the ground water, which faces a serious challenge due to, two reasons, first, is the overuse, and over pumping, while the second is the attack of the salt water due to the Mediterranean Seawater level rise, because of the climate changes. These two reasons must be overcome, if the first reason can be controlled by law, and technical roles, the second reason needs intensive studies and investigations concerning the interaction between seawater and fresh ground water.

In such problematic water situation in Egypt, control and saving of the available limited quantity takes great importance from both technical and national points of view. In addition to all the well-known traditional reasons of the problem such as pollution, over usage, and bad traditions of dealing with water, a new very important reason is added nowadays, called "Climate Changes" which has a direct impact on sea water rising, that causes a serious attack of the salt water to the fresh water especially in River Deltas., Not only the surface water, but also the ground water. Since that process proved some acceleration, several investigations have recently considered the worst impacts of climate change and sea water level rise on sea water intrusion. Most of them have revealed the severity of such problem, and the significance of the land movement of the dispersion zone under the sea water level rise situation. In this paper, we try to introduce a technical review and study for the most popular studies concerning our topic, and its most important conclusions, as an approach for preparing the Ph.D. thesis about the Nile Delta water equilibrium in the light of the expected Mediterranean Sea water level rise. Nile Delta, which located between Damietta Branch on the East, and Rosetta Branch on the west, occupies about 20000 square kilometers of the most rich, productive land in Egypt. About 50% of Egyptian population live in that area, agriculture is the main human activities on them, so water is the prime factor in their life, and their agriculture investments. The great amount of this investment depends on the ground water, which faces a serious challenge due to, two reasons, first, is the overuse, and over pumping, while the second is the attack of the salt water due to the Mediterranean Seawater level rise, because of the climate changes. These two reasons must be overcome, if the first reason can be controlled by law, and technical roles, the second reason needs intensive studies and investigations concerning the interaction between seawater and fresh ground water.

Since inclined headwalls proved promising good results in increasing the performance efficiency of the under-desert road culverts, and so protecting such roads against overtopping and flooding (Ashour et al., 2016). Using headwalls with inclination angle less than 45° will be so expensive due to its big length for reaching the water levels, so in this experimental study, we present a trial for introducing an economical solution for using such inclined headwalls, to score the two needed goals (more culvert performance efficiency, for desert roads protection and at the same time, with minimum cost). The technical idea tested here is to use a broken headwall consists of two parts; the first part is an inclined part just over the top point of the culvert, while the second part which will be over that inclined part will be vertical and extends some distance over the water surface. This study is divided into two trends, the first one is focusing on obtaining the optimum inclination angle (θ), of the inclined lower part of the tested headwall, and the second trend concerns with the length (L) of that inclined part (as a function of the culvert inside height "d") after which the vertical part begins. Six angles of inclination ranging from 15° to 90° were tested in addition to the culvert without any headwalls (projected culvert) as a reference. In the second pivot, five models of broken headwalls of lower inclined part of length ranging as L/d = 0.5, 1.0, 1.5, 2.0, and 2.5 were examined with the recommended inclination angle. Experiments carried out using the introduced new shape of the headwall in both upstream and downstream sides (at the entrance and exit of the culvert). Through a total of 315 experimental runs, 30° inclination angle for the introduced headwall in both culvert's entrance and exit, proved the best among all the tested angles. Also, the relative length of the inclined part (L/d) =2.5 showed the best economic relative length for the lower inclined part among all the tested relative lengths.

Since inclined headwalls proved promising good results in increasing the performance efficiency of the under-desert road culverts, and so protecting such roads against overtopping and flooding (Ashour et al., 2016). Using headwalls with inclination angle less than 45° will be so expensive due to its big length for reaching the water levels, so in this experimental study, we present a trial for introducing an economical solution for using such inclined headwalls, to score the two needed goals (more culvert performance efficiency, for desert roads protection and at the same time, with minimum cost). The technical idea tested here is to use a broken headwall consists of two parts; the first part is an inclined part just over the top point of the culvert, while the second part which will be over that inclined part will be vertical and extends some distance over the water surface. This study is divided into two trends, the first one is focusing on obtaining the optimum inclination angle (θ), of the inclined lower part of the tested headwall, and the second trend concerns with the length (L) of that inclined part (as a function of the culvert inside height "d") after which the vertical part begins. Six angles of inclination ranging from 15° to 90° were tested in addition to the culvert without any headwalls (projected culvert) as a reference. In the second pivot, five models of broken headwalls of lower inclined part of length ranging as L/d = 0.5, 1.0, 1.5, 2.0, and 2.5 were examined with the recommended inclination angle. Experiments carried out using the introduced new shape of the headwall in both upstream and downstream sides (at the entrance and exit of the culvert). Through a total of 315 experimental runs, 30° inclination angle for the introduced headwall in both culvert's entrance and exit, proved the best among all the tested angles. Also, the relative length of the inclined part (L/d) =2.5 showed the best economic relative length for the lower inclined part among all the tested relative lengths.

The compatibility between the needed structural designed dimensions of the irrigation works and the dimensions of the water stream or the canal in which the irrigation work will be located has a great importance from more than one point of view. As it is well known, the main aim of the designer of such works is to reach the optimum design for maximum performance efficiency with economical cost, and minimize negative technical impacts that may be harmful to the safety of the whole work. Since the complete suitability between the obtained designed dimensions of the different construction elements of the work, and the original properties and dimensions of the canal in which the work will be constructed, is rarely occurring. The designer always has to make some changes in the original engineering properties and dimensions of canals, such as bed width, bed level, and/or inside side slope, to reach the needed suitable compatibility between the structural design and the natural original canal cross section. For the economical purposes, the design always needs less width of the work, than the width of the bed of the original stream cross section, so a contraction may be needed where the work will be constructed; the literature indicated that, such a contraction must not be less than 0.6 of the original bed width. That contraction, of course, has a direct impact on the different hydraulic parameters, such as water depth, velocity, and flow regime in the location of the work. Changes of such hydraulic parameters may exceed their safe permissible values, and so the whole structure may face some dangerous situations, which must be overcome. In this paper, we present a technical survey of the previous research concerning canal width contraction, with the needed technical comments, and comparisons as a logical approach for a master-thesis under the same title.

The compatibility between the needed structural designed dimensions of the irrigation works and the dimensions of the water stream or the canal in which the irrigation work will be located has a great importance from more than one point of view. As it is well known, the main aim of the designer of such works is to reach the optimum design for maximum performance efficiency with economical cost, and minimize negative technical impacts that may be harmful to the safety of the whole work. Since the complete suitability between the obtained designed dimensions of the different construction elements of the work, and the original properties and dimensions of the canal in which the work will be constructed, is rarely occurring. The designer always has to make some changes in the original engineering properties and dimensions of canals, such as bed width, bed level, and/or inside side slope, to reach the needed suitable compatibility between the structural design and the natural original canal cross section. For the economical purposes, the design always needs less width of the work, than the width of the bed of the original stream cross section, so a contraction may be needed where the work will be constructed; the literature indicated that, such a contraction must not be less than 0.6 of the original bed width. That contraction, of course, has a direct impact on the different hydraulic parameters, such as water depth, velocity, and flow regime in the location of the work. Changes of such hydraulic parameters may exceed their safe permissible values, and so the whole structure may face some dangerous situations, which must be overcome. In this paper, we present a technical survey of the previous research concerning canal width contraction, with the needed technical comments, and comparisons as a logical approach for a master-thesis under the same title.

Uplift is one of the main design factors for heading up works. This fact occupied the attention of many investigators in recent decades. The work presented herein comes as a trial for investigating the effect of arrangement of cutoffs and their depths on the uplift forces under the floor of diversion and head water structures. Cutoffs are one of the most important methods for decreasing the uplift forces if located at the right positions. Such positions are usually the beginning, the end of the solid apron, under the main heading up structure or combinations of them. The present study introduces an experimental investigation to clarify the precise behavior of the uplift forces due to the above mentioned locations. So, the experiments were carried out by providing the floor with one or two of cutoffs with different depths and locations. However, the sum of the total depths of the cutoff is kept constant and equal 20% of the floor length. The cutoffs were arranged in their locations to be at the beginning, end of the floor, or in-between to detect their effects on the uplift pressure. The obtained results for the studied cases proved that; for a fixed cut off depth, the nearer the location of such cutoff to the upstream the bigger the reduction of uplift distribution affecting the rest of the solid apron length. When the cutoff is used at the end of the floor, the reduction of the uplift force is not significant although its positive influence on exit gradient. The best location of cutoffs giving maximum uplift reduction is obtained. The results give a clear picture about the uplift distribution in longitudinal directions.

Uplift is one of the main design factors for heading up works. This fact occupied the attention of many investigators in recent decades. The work presented herein comes as a trial for investigating the effect of arrangement of cutoffs and their depths on the uplift forces under the floor of diversion and head water structures. Cutoffs are one of the most important methods for decreasing the uplift forces if located at the right positions. Such positions are usually the beginning, the end of the solid apron, under the main heading up structure or combinations of them. The present study introduces an experimental investigation to clarify the precise behavior of the uplift forces due to the above mentioned locations. So, the experiments were carried out by providing the floor with one or two of cutoffs with different depths and locations. However, the sum of the total depths of the cutoff is kept constant and equal 20% of the floor length. The cutoffs were arranged in their locations to be at the beginning, end of the floor, or in-between to detect their effects on the uplift pressure. The obtained results for the studied cases proved that; for a fixed cut off depth, the nearer the location of such cutoff to the upstream the bigger the reduction of uplift distribution affecting the rest of the solid apron length. When the cutoff is used at the end of the floor, the reduction of the uplift force is not significant although its positive influence on exit gradient. The best location of cutoffs giving maximum uplift reduction is obtained. The results give a clear picture about the uplift distribution in longitudinal directions.

Uplift is one of the main design factors for heading up works. This fact occupied the attention of many investigators in recent decades. The work presented herein comes as a trial for investigating the effect of arrangement of cutoffs and their depths on the uplift forces under the floor of diversion and head water structures. Cutoffs are one of the most important methods for decreasing the uplift forces if located at the right positions. Such positions are usually the beginning, the end of the solid apron, under the main heading up structure or combinations of them. The present study introduces an experimental investigation to clarify the precise behavior of the uplift forces due to the above mentioned locations. So, the experiments were carried out by providing the floor with one or two of cutoffs with different depths and locations. However, the sum of the total depths of the cutoff is kept constant and equal 20% of the floor length. The cutoffs were arranged in their locations to be at the beginning, end of the floor, or in-between to detect their effects on the uplift pressure. The obtained results for the studied cases proved that; for a fixed cut off depth, the nearer the location of such cutoff to the upstream the bigger the reduction of uplift distribution affecting the rest of the solid apron length. When the cutoff is used at the end of the floor, the reduction of the uplift force is not significant although its positive influence on exit gradient. The best location of cutoffs giving maximum uplift reduction is obtained. The results give a clear picture about the uplift distribution in longitudinal directions.