Irrigation
H. Shokati; Z. Sojoodi; M. Mashal
Abstract
Introduction Arid and semi-arid climates prevail in Iran. The precipitation is also sparsely distributed in most areas of the country. Therefore, there is a need for management measures to overcome the water crisis. One of these measures is designing rainwater harvesting systems that can meet some ...
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Introduction Arid and semi-arid climates prevail in Iran. The precipitation is also sparsely distributed in most areas of the country. Therefore, there is a need for management measures to overcome the water crisis. One of these measures is designing rainwater harvesting systems that can meet some of the non-potable needs and reduce runoff in urban areas. The main components of rainwater harvesting systems in residential regions include the catchment area, storage tank, and water transfer system from the catchment area to the tank. The storage tank is the biggest investment in a rainwater harvesting system, as most buildings are not equipped with a storage system. Therefore, tank capacity should be determined optimally to minimize project implementation costs. The stored water volume and the project profit increases with increasing the tank volume. However, in this case, the price of the tank increases. Therefore, the tank capacity should be optimally designed to justify economic exploitation.Materials and Methods In order to evaluate the feasibility of using rainwater harvesting systems, the tanks’ volume was optimized. Due to the higher rainfall of Ardabil relative to the average rainfall of the country, it is expected that this area has a good potential for the implementation of rainwater harvesting systems. Therefore, this region was selected as the study area under the scenario of a residential house with 100 and 200 m2 catchment areas and four inhabitants. The amount of rainfall in the region is one of the primary parameters in determining the volume of rainwater collection tanks. Some of the precipitated water is always inaccessible due to evaporation from the surface. Nonetheless, since there is almost no sunlight during and immediately after rainfall, and also the received water enters the reservoirs shortly after precipitation, evaporation was assumed to be zero. Daily precipitation data for 42 years (from 1977 to 2019) were retrieved from the Ardabil Meteorological site. The daily water balance modeling method was used to analyze the rainwater harvesting systems due to the simplicity of interpretation, high accuracy and better general acceptance. Daily precipitation data were entered into this model and used as the primary source to meet the domestic demands. Simulation of rainwater harvesting systems was performed using daily precipitation data in MATLAB software, and the reliability of these systems was calculated for different tank volumes. Then, considering the price of drinking water and the current price of tanks in the market, the optimal volume of tanks was calculated using the Genetic Algorithm. Finally, the annual volume of water supply and the amount of water savings in case of using the optimal volumes of tanks were also estimated.Results and Discussion The results showed that the percentage of reliability is directly related to the volume of the tank, thus, the reliability percentage also increases with increasing the tank capacity. As the volume of the tank increases, the slope of the increasing reliability percentage decreases continuously, to the point that this slope becomes almost zero. Comparing the reliability percentage obtained for 100 and 200 m2 rooftops indicated that 200 m2 rooftop had a higher reliability percentage than 100 m2 rooftop due to receiving much more rainfall and meeting the water need for a longer duration. By comparing the results of overflow ratio for 100 and 200 m2 rooftops, it can also be concluded that using a fixed size tank, the overflow in 200 m2 rooftop is higher, which is due to receiving more water volume than 100 m2 rooftop. The results also showed that by using a 5 m3 tank, 44.5 and 24 m3 of water can be stored annually from the 200 and 100 m2 catchment areas, respectively, these are equal to 28 and 19 m3, respectively, if 1 m3 tank is used. The optimal tank volumes for 100 and 200 m3 rooftops are equal to 0.59 and 1.66 m3, respectively. Since the tanks are made in specific volumes, the obtained volumes were rounded to the closest volumes available in the market. Thus, a 1.5 m3 tank was used for a 200 m2 rooftop and a 0.5 m3 tank was applied for a 100 m2 rooftop.ConclusionApplication of a tank of 0.5 m3 for the rooftop of 100 m2 was the most profitable for saving 17% of water consumption, annually. Moreover, the optimal tank volume for the 200 m2 rooftop was selected to be 1.5 m3, saving about 32 % of water consumption per year. Water-saving percentages indicate the high potential of our study area for the implementation of rainwater harvesting systems.
Irrigation
Z. Sojoodi; H. Shokati; Y. Sojoodi; M. Mashal
Abstract
IntroductionThe constructive effects of green spaces on the quality and livability of the urban environment have been reported in many studies. Therefore, using methods that can accurately estimate the evaporation of transpiration in green space can help to reduce water loss. The purpose of estimating ...
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IntroductionThe constructive effects of green spaces on the quality and livability of the urban environment have been reported in many studies. Therefore, using methods that can accurately estimate the evaporation of transpiration in green space can help to reduce water loss. The purpose of estimating water demand for urban green space is also different from the purpose of determining water demand for an agricultural farm. In urban green space, the goal is to maintain good growth, appearance and acceptable plant health, while biomass production is the main goal on agricultural farms. Therefore, urban green space can typically be managed using an irrigation area that is less than the amount of water needed to produce agricultural products. Due to the limited water resources in arid areas, the use of less irrigation in urban green space can be desirable to save water consumption.Materials and MethodsThe Wucols method for estimating Water requirements in green space was developed by Castello et al. (4). They developed the Wucols water taxonomy guidelines for planting green space in California. The Wucols method estimates evapotranspiration in green space using reference evapotranspiration and a set of coefficients (Species factor, density factor and microclimate factor). PF method is the minimum acceptable irrigation for green space plants that emphasizes maintaining the beauty of the plant. In this method, the water required by green space plants is considered as a percentage of ET0 so as not to reduce their appearance and performance. In this approach, PF is a regulatory factor that is actually considered instead of Kc and multiplied by ET0, except that the emphasis is on the appearance of the plant and not on its optimal growth and yield. The IPOS method has been developed by the Government of South Australia for planning and managing water needs in public open spaces, especially sports lawns and amusement parks. In this method, the water requirement of grass in urban open space is calculated. In this method, plant transpiration evaporation (ETL) is calculated by multiplying reference transpiration evaporation factors (ET0) by grass vegetation coefficient (Kc) by plant stress factor (Kst).Results and DiscussionThe results showed that the highest rate of evapotranspiration obtained by Wucols method was 83.38 mm during 21 Jun-21 Jul. Also, the rate of transpiration evaporation during one year of the experimental period was estimated to be 556.5 mm. The results of estimation of transpiration evaporation by PF method also show the maximum amount of transpiration evaporation during 21 Jun-21 Jul and is 75.55 mm. The evapotranspiration rate during one year was estimated to be 505.9 mm. For the Ipos method, the highest rate of transpiration evaporation was estimated to be 36.38 mm during 21 Jun-21 Jul and 242.9 mm during the experimental period. Gross irrigation requirement is estimated by considering 70% irrigation efficiency for each month using all three methods. For the Wucols method, the gross irrigation need during one year was estimated to be 794.8 mm. For the PF method was 722.7 mm and for the IPOS method was 346.9 mm. According to the reported irrigation records for the study area, which is 900 mm per year, the Wucols method has the closest result to the irrigation records.ConclusionThe results showed that the Wucols method has the best and closest estimate according to the irrigation records of the study area. The gross irrigation requirement calculated by the Wucols method during a year is 794.8 mm, which is 12% less than the gross annual irrigation requirement of the studied green space. While PF and IPOS methods determined the amount of gross demand 20 and 62% less than the annual irrigation rate in the region, respectively. The results of this study show that the Wucols method for estimating the water requirement of plants in urban green space where there is a combination of different plant species is more reliable than the PF and IPOS methods due to the diversity of species, vegetation density and different climates.
