Water Productivity Journal
Volume:1 Issue: 1, Summer 2020

The knowledge about soil evaporation is essential for improving water productivity (WP) in water-limited regions. Evaporation front (EF) depth and intensity (EI) are the most important components of agricultural activities and environmental issues, the physical characteristics of soil play a significant role in these fields. One of the key elements in physical soil properties is the relationship between the depth of the static surface and evaporation from the soil surface, especially in arid and semi-arid regions. In these regions, due to over-irrigation, the water level is very close to the ground surface which leads to salinization of the soil. The same situation may also be observed on the banks of lakes and rivers. In the present study, the EF depth and the EI of three different types of soil textures including sandy loam, loam, and clay loam are simulated in 30 cm, 40 cm, 70 cm static levels by using Gardener model. The findings of the study reveal that after 77 days, the EF depths were 6.14, 7.85, and 13.86 cm for sandy loam soil, 5.23, 7.27, and 12.2 cm for loam soil, and 5.4, 7.2, and 10.9 cm for clay loam soil in three static levels (i.e. 30, 40, and 70 cm), respectively. The deeper the static level, the deeper the depth of EF. Simulation of EF depth for sandy loam soil regarding loam and clay loam soils have more correspondence with the measured depth of the evaporation front. The measured and simulated amounts of EF depth and EI in three soil textures with three water levels were stabilized and compared by the F-statistical test models. Comparing the evaluated data of EF with the simulated figures of the evaporation front in textures and diverse static levels using the statistical test showed that a one to one line at a significant level of 5% is suitable for sandy loam soil.

Global climate change and its effect on water resources have further reduced the amount of water available for agriculture. Under this circumstance, the use of pressurized irrigation systems can be an option of enhancing the efficiency of water consumption. The mobile rain gun is very useful equipment which can be used for irrigating large areas and it works at a minimum pressure of 2kg/cm². The mobility of the equipment is possible at minimum pressure of 6kg/cm² pressure. For the calculation of uniformity in irrigation catch can test were conducted at various pressure by using various nozzle. The Christiansen’s equation for uniformity was used for calculation purpose. The grid is plotted for the spacing 3x3 meters and it covers an area of about 360m². The maximum uniformity was noted in the 12mm nozzle at 2kg/cm² pressure. The uniformity is much reduced for the high pressure due to wind drift and pressure fluctuations. The contour graphs were also used to find out the area of highly uniform distribution. The tape was used for measuring the throw range of rain gun during operation. The throw range varies from 8 to 30m for 10mm at 2kg/cm² and 14mm at 6kg/cm² respectively. The distribution graph was drawn to find out the change in distribution of water along with the change in distance from the rain gun. The rain gun is designed to irrigate large area by using a single unit so the distribution is more for large ranges compared to the places which are nearer to the implement. One of the major problem occur during the sprinkler irrigation is evaporation loss of spraying water. The distribution of water depended upon the things like pressure, climatic condition, wind speed, wind direction and the temperature.

Oil and gas drilling produce saline brine, posing a threat and great risk to the environment. Desalination is a pathway to freshwater production and brine removal, however, the energy required for processing and highly concentrated brines curtail the approach. Solar desalination humidification dehumidification (SDHDH) systems are a low energy and economical response that solves the problems. The current study aims to demonstrate saltwater solar-desalination, an innovative SDHDH design, used to process the waste materials. The method was successfully tested at full scale as follows: In a 400 m2 application containing 600 m3 saline-water, the total dissolved solids (TDS) were equal to 141 g l-1, requiring an input of 196.2 kW electrical energy. As a result of SDHDH 266 m3 of freshwater was obtained, with TDS equal to 210 mg l-1. The water-recovery percentage achieved was 44%. The salt removal efficiency was near 100%. Surface-time efficiency varied, between 8 to 30 l m-2day-1. SDHDH use is an effective mechanism to elute freshwater from concentrated brines, maximizing productivity, and lowering hazardous impact to the environment providing benefits to ecosystem and human services alike.

Soil water retention curve is among the most important properties needed for many soil and water management purposes. Due to high spatial and temporal variability in soils, its direct measurement is rather difficult, time consuming and expensive. Consequently, it would be more feasible to estimate it by using some indirect mathematical methods. The objectives of this investigation are to (1) determine the fractal dimension of the soil retention curve by fitting fractal models to the measurements and (2) investigate the relationship between the fractal dimension and other physical/textural/hydraulic parameters such assoil particle fractions of clay, silt, and sand in large scale. For this purpose, 190 soil samples with broad range of textures from four large agricultural areas were collected, and their particle size distribution, bulk density, organic carbon, salinity, pH, and retention curves were measured. To evaluate the performance of examined fractal models, three statistical parameters including RMSE, RMSD and R2 were used. Results indicated that the fractal dimension has an inverse relationship with soil texture; the finer the soil texture, the greater the fractal dimension. The lowest and greatest fractal dimensions of the Tyler-Wheatcraft model in loamy sand and clay textures were obtained to be 2.38 and 2.74, respectively. These were significant at 1% level based on the Duncan’s multiple range tests. Results further showed that the most accuracy of estimating retention curve in different soil textures by using van Genuchten, Brooks-Corey, and Tyler-Wheatcraft with normalized errors average obtained were 0.06, 1.09, and 3.27, respectively. Furthermore, the obtained R2 values were ranged from 0.88 to 0.99 for Tyler-Wheatcraft and van Genuchten models, respectively. Compares to Brooks-Corey model, the van Genuchten retention model provided better accuracy in estimating retention curve for different soil textures.

This study seeks to assess the effects of climate change on the agriculture sector across a number of Southern  Mediterranean countries and evaluate relevant policy measures addressing these challenges for the region. Agriculture is dependent on land and water use, and key activity for rural populations over large areas in Southern Mediterranean Countries. Water resources are essential to a stable agricultural production, but also to the supply of growing cities. In this region, it is likely that the stress imposed by climate change to agriculture has contributed to the reduction water availability. Adaptation is a key factor that will shape the future severity of climate change impacts on food production. Food and nutrition security presents a significant challenge for these Southern Mediterranean countries. Agriculture, which accounts for 70 percent of all water uses, is increasingly required to ‘make its case’ for its share of water to enable food production and ensure food security. At the same time, the sustainability of agricultural water use is under increasing scrutiny. In recent decades, attempts to solve the growing water issues have focused on management issues without considering the governance dimension, and mostly on a sectoral basis. While successful in many ways, this approach seems to have reached its limits. This paper describes the first comprehensive assessments of climate change and its impacts in Eastern and Western Mediterranean Countries, covering different sectors, ranging from physical climate drivers as temperature and precipitation, to agriculture, forests, and from water resources to social impacts and policy evaluation. The evidence provided suggests the need for more effective adaptation measures for the agriculture sector across Eastern (Egypt, Israel, Jordan, Lebanon and Palestine) and Western (Algeria, Morocco and Tunisia) of south Mediterranean countries. Southern Mediterranean Countries are affected by climate change. This is associated with increases in the frequency and intensity of droughts and hot weather conditions. Since the region is diverse and extreme climate conditions are already common, the impacts are disproportional. The impacts of climate change on Southern Mediterranean Countries water resources are significant. Climate induced changes in precipitation and air temperature lead to earlier timing of peak flows, greater frequency of flooding, and more extreme drought conditions. Rainfall in these countries is even expected to increase in winter, while decreasing in spring and summer, with a substantial increase of the number of days without rainfall. Anticipated regional impacts of climate change include heat stress, associated with poor air quality in the urban environment, combined with increasing scarcity of fresh water and decreasing water productivity in arid regions. This study seeks to assess the effects of climate change on the agriculture sector across a number of southern Mediterranean countries and evaluate relevant policy measures addressing these challenges for the region.

The purpose of this study was to determine the quantitative effect of management of public institutions in promoting optimal water consumption and reducing operating and maintenance costs. For this purpose, two farms with of 48 and 49 (ha) area, which cultivated with an approved cultivation pattern (40% autumn + 60% spring) were selected in two separate canals. The selected farms are irrigated by a rotating sprinkler irrigation system (center pivot). The water requirement of the mentioned systems was estimated using Netwat software and the operation of these machines was done in accordance to the relevant instructions and network design principles. The legal organization (Rural Production Cooperative) in charge of the farm #1 (48 ha) complied with the management and technical rules in relation to the second organization (in charge of the farm #2 with 49 ha) with a regular structure. Necessary calculations of irrigation efficiency were carried out according to the values recorded in the input meters of both devices and the cost of operation, maintenance, repairs and protection. Finally, the irrigation efficiency of the first and second farms were obtained 75% and 55%, respectively. Operating and maintenance costs were also reduced by 30%. The results indicated that the human and structural management have an important role in the irrigation and drainage sub-network planning.

This work compares the performance of a solar still during winter and summer months for purification of salty water, suiting arid conditions to produce distilled water. To ensure zero energy cost, the apparatus is completely run on ambient solar energy pipes for water circulation and heating, without any pumping requirement. The performance of the unit is evaluated over daylight hours under standard operating conditions during summer where sunshine is almost at its peak. However, the design of the solar still is modified to enhance the heating rate inside the solar basin during winter months with low ambient temperature through the attachment of a solar pipe warm water circulation into the water basin, which was fed by solar panel system water heating units. The water circulation from the basin to the solar collectors is solely due to the temperature difference and no pumping is required to increase the flow of water. The modified arrangement was found to achieve a temperature inside the water basin of over 50°C on a typical winter day when the ambient temperature was as low as 9°C. This resulted in the maximum amount of produced condensate yield reaching up to 2 l/hr, which was found to exceed the typical yield of 1.5 l/hr under summer conditions.