There is consensus on the impact of wastewater irrigation on soil properties and heavy metal accumulation. The studies that show the impact of temporal changes as a result of different long-term additions of wastewater on the heavy metal accumulation and degradation of soil are extremely limited. This study was carried out to assess heavy metal contamination in soils irrigated with wastewater for more than 30 years in Egypt. A total number of 12 irrigation water samples and 12 soil profiles were collected during 2020 and were chemically characterized. The results showed that soils irrigated with wastewater over the long term contained significantly higher concentrations of heavy metals compared to fields irrigated with fresh water. Heavy metal levels in water and soil samples were within the permissible limits, with the exception of Cd concentration in water (0.03 mg L⁻¹). Continuous cultivation for a long period of time (30 years) using raw urban wastewater application has led to the adverse effect of increasingly available Pb concentration (5.44 mg kg⁻¹). Similar temporal behavior was seen for Cd and Fe, which increased by 0.98 and 11.2 mg kg⁻¹, respectively, after 30 years. The heavy metals in wastewater-irrigated soils significantly increased in clayey soils, as compared to sandy soils irrigated from the same source. Our findings provide important information for decision makers in Egypt and similar countries for the development of a strategy for the use of wastewater in irrigation for sustainable agricultural management.

The shortage of water is a major obstruction to the social and economic development of many countries, including Egypt. Therefore, there is an urgent need to properly manage water resources to achieve optimum water use. One way of saving available water resources is to reduce evaporation that leads to the loss of a large amount of water from reservoirs and open lakes. This paper aims to use a floating photovoltaic system (FPVS) to cover a lake’s water surface to reduce evaporation and also for energy production. This methodology was applied to Lake Nasser as one of the largest lakes in the world where much evaporation happens due to its large area, arid environments, and the shallow depths of some parts of the lake. The estimated evaporation from the lake was 12.0 × 10⁹ m³/year. The results show that covering 25%, 50%, 75%, and 100% of the lake can save about 2.1, 4.2, 6.3, 7.0, and 8.4 × 10⁹ m³/year and produce energy of 2.85 × 10⁹, 5.67 × 10⁹, 8.54 × 10⁹, and 11.38 × 10⁹ MWh/year, respectively. Covering areas of shallow water depth was more efficient and economical. The results show that covering 15% of the lake’s area (depths from 0.0 to 3.0 m) can save 2.66 × 10⁹ m³/year and produce 1.7 MWh/year. Covering 25% of the lake’s area (depths from 0.0 to 7.0) can save 3.5 × 10⁹ m³/year and produce 2.854 MWh/year. Using an FPVS to cover parts of Lake Nasser could help manage water resources and energy production for Egypt to overcome the likely shortage of water resources due to population growth. This system could be applied in different locations of the world which could help in increasing water resources and energy production, especially in arid and semi-arid regions.

Evaluating water quality indicators is a crucial issue in integrated water resource management, since potable water is an essential resource for the world’s health and sustainable development. The current study was developed using a coupled model of MODFLOW and MT3DMS (Mass Transport 3-Dimension Multi-Species) to integrate two water supply systems, surface water (polluted drains and canals) and ground water, to identify the contamination process of the groundwater from drains as fresh water is polluted and the contamination level exceeds the standard limits. The study was applied to two cases: the first was a hypothetical simulation and the second was the real case of the Nile Delta Aquifer (NDA). Four different scenarios were simulated to first identify groundwater contamination by total dissolved solids (TDS), and then select the more efficient protection process. The first scenario involved changing polluted drain and canal boundary conditions regarding head and concentration; the second consisted of studying the location of the polluted drain in a low permeability layer or a confined aquifer; the third was based on installing a cut-off wall in the polluted drain sides; and the fourth investigated the use of lining materials for polluted drains. The results reveal that aquifer contamination was decreased by increasing the water head of canals by 50 cm and decreasing the drain head by 50 cm and concentration by 25%, whereby large quantities of groundwater were protected. The percentages of salt repulsion in the hypothetical case were +10.66, +12.89, and +24.99%, while in NDA they were +6.29, +8.71, and +25% respectively compared with the base case. Decreasing the aquifer hydraulic conductivity led to decrease in aquifer contamination, in which the confined aquifer pollution was less than the unconfined aquifers due to the clay cap, which plays a significant role in minimizing the solute transport into the groundwater reservoir, and to reduction of the aquifer salt variation by +19.01% for the hypothetical case. The results indicate that the cut-off wall is effective for contamination management in shallow aquifers (hypothetical case) and the reduction in aquifer salt was +28.49%, whereas it had no effect in the deep aquifer (NDA), where the salt was reduced by just +0.34%. Using the drain lining scenario prevented contamination from the polluted drains and protected the freshwater in the aquifer, so that the aquifer salt mass reductions were +91.02 and +70.13% for the hypothetical case and NDA respectively, indicating that this method is more effective for controlling groundwater contamination. Polluted drains should be located in a low permeability layer to minimize the water degradation. This study represents a new contribution to groundwater protection techniques by changing the boundary conditions, installing a cut-off wall and using linings for polluted drains, and shows the way forward for the future treatment of polluted stream networks.

Urban growth is one of the major causes of flooding in urban areas. This affects the runoff coefficients, which is among the most important factors that affect the design of storm water drainage systems. Changing the runoff coefficient will affect the design parameters of the drainage network, including outfall discharge, velocity, lag time and cost of construction. This study aims to assess the effect of changing the runoff coefficient due to urban growth on the design of a storm water drainage system. The hydrological models Hyfran, StormCAD and GIS are used to analyze different runoff coefficients. This study examines three zones in Dammam in the Kingdom of Saudi Arabia (KSA). The data developed from the models for the current case studies are used to develop an empirical equation to predict the max discharge for other catchments. The discharge is a function of the return period, runoff coefficient, drainage density, longest path, rainfall intensity and catchment area. To validate the developed equation, we use it to estimate the discharge in a real case study in South Korea. A comparison between the measured discharge and estimated discharge shows that the empirical equation is capable of predicting the maximum discharge for different catchments with high accuracy. Then, the validation of the models is carried out to determine the effect of the runoff coefficient on the design of a storm water drainage system in a case study in KSA. The results show that an increasing runoff coefficient due to urban growth increases the outfall discharge and velocity of storm water drainage systems, as well as affecting the cost of construction and decreasing the lag time. The cost increases by two to three times with increasing urbanization. This study provides a new perspective on the hydrologic impact of urban growth on the design of storm water drainage systems, which are essential for flood management. Moreover, the relationship between urban growth and the cost of storm drainage networks is explored, which could help decision makers to make appropriate judgements.

This study aims to investigate the impact of using untreated wastewater in irrigation. Different scenarios of management were applied by mixing it with treated wastewater or freshwater on groundwater quality. A hypothetical case study is presented. The numerical model of MODFLOW is used in the simulation by applying four stages (21 scenarios) including: different values of pumping rates, changing wastewater recharge rates, and a combination of the previous scenarios. Additionally, protection scenario for groundwater was applied by using different values of mixing of freshwater with wastewater. The simulation was carried out for the contamination of Chemical Oxygen Demand COD and the concentration reached 48.6 ppm at a depth of 25 m and 19.41 ppm at a depth of 50 m in the base case. The results showed a negative impact on groundwater quality had occurred due to increasing the pumping rates, wastewater recharge rates, and combination between two scenarios, which led to an increase of the contaminants in the aquifers. However, positive protection effects occurred due to mixing the wastewater with treated wastewater. The results of COD concentration in groundwater using treated wastewater reached 81.82, 77.88, 74.03, 70.12, and 66.15 ppm at a depth of 25 m and 53.53, 50.95, 48.43, 45.87, and 43.28 ppm at a depth of 50 m, at concentrations of 93, 88.52, 84.14, 79.7, and 75.19 ppm with constant pumping and recharge rates of 4320 m³/d and 547.5 mm/year, respectively. The using of treated wastewater could improve the groundwater quality to be used in the irrigation process and help to minimize groundwater contamination. Moreover, the abstraction of the groundwater should be optimized, and the qualities of wastewater should be constrained in agriculture to protect the groundwater quality.

In this paper, the results of trend analysis applied to precipitation and temperature monthly data for the period from 1962 to 2014 is presented for the hydrological year (from November to October) in sixteen climatic stations in Eastern Slovakia. The topography of this part of the country is very diverse and it affects the climate. The Mann-Kendall non-parametric test coupled with Sen’s slope was applied to identify the significant long-term climatic trends, as well as the magnitude of those trends. According to the present study, all climatic stations in Eastern Slovakia show a positive trend in temperature during the year and almost all of them show a significant positive annual trend in temperature. Seasonal and monthly trend analyses produced the same results. Trends in temperature are always positive during winter and spring. Trends in precipitation are also mostly positive during winter and spring, although some negative trends were also found during these seasons. The spatial distribution of precipitation and temperature trends was modelled in ArcGIS using geostatistical analysis. Abrupt positive trend shifts in annual precipitation and temperature time series were also investigated. An abrupt shift in precipitation at the highest climatic station, Lomnický peak, began around 1985 (+). Abrupt shifts in temperature began around 1970 (+) at the presented climatic stations. The extremity of the climate is confirmed by an analysis of the trends in wet and dry spells. Trends showed increasing tendencies in medium- and long-term wet spells.