نشریه مدیریت آب در کشاورزی
سال ششم شماره 1 (پیاپی 11، بهار و تابستان 1398)

The access to fresh groundwater is playing an imporatant role for sustainable crop production and secure livelihood of people living in the Neyshabour plain. Decline in groundwater table and aquifer fractional are the most important challenges in this plain. In the Neyshabour plain about 84 thousand hectares of agricultural land are cultivated annually and more than 90% of groundwater resources are used in the agricultural sector. In this paper, Soil-Water-Atmosphere-Plant (SWAP) model is calibrated and validated using measured field data from six different fields located in the Neyshabour plain. For this purpose, field information and other SWAP requirement data were collected in the six farm conditions. Calibrated and validated SWAP model is then used to quantify the effects of existing irrigation practices on water balance components and different water productivity indicators for wheat, barley, sugar beet, cotton, silage corn and tomato. Also, the effect of applying the two senarios (1. 20-30% reduction of water consumption during growth period, 2. removal of irrigation intervals in the non-sensitive plant growth stage) was estimated on the reduction of exploiting of groundwater resources. The results showed that under the current irrigation practices, soil evaporation reduced WPET (Yact/ETact) over WPT (Yact/Tact) by 24%, 26%, 27%, 21%, 8% and 15% for wheat, barley, sugar beet, cotton, silage corn and tomato, respectively. The reduction in WPETQ (Yact/ETact+qbot) over WPET because of deep percolation was even higher and remains 50%, 44%, 33%, 37%, 14% and 53% for wheat, barley, sugar beet, cotton, silage corn and tomato, respectively. The substantial differences in WP values emphasized the need to control non-beneficial soil evaporation and deep percolation losses, and change traditional irrigation system by a more efficient one. Applying deficit irrigation management for the six major crops in the neyshabour plain resulted in a 27% reduction in the extracting of groundwater aquifer with a change in yield +4 to -17%. This less withdrawal amount is equal 105 million cubic meters of exploiting of groundwater and compensates for 77% of the reservoir fraction in the Neyshabour plain. Removing an irrigation turn for six malor crops in the Neyshabour plain causes a 17.5% reduction in exploiting from groundwater aquifer with a decrease in yield from 4 to 10 percent. This amount of discharge is equivalent to saving 69 million cubic meters of groundwater, thus compensating about 50% of the groundwater aquifer fraction.

This study conducted in order to assess accurate of Aquacrop Model in yield grain and Biomass simulation under rice(Hasham cultivar) deficit and saline irrigation management conditions in Rasht Rice Research Institute of Iran, during two year from 2009-2011. This experiment was conducted in form of factorial randomized complete block design with 3 replications. Treatments consisted of 4 levels of salinity as follows: S1, tap water with salinity less than 1 dS m, S2, S3, S4, respectively salinity of 2, 4, 6 dS m and five irrigation methods include I0: Irrigation continuous, I1, I2, I3, I4, respectively, in water saturation (AWD), irrigation at field capacity (FC), irrigation water content of 100, 90 and 80% of field capacity. AquaCrop model was evaluated for rice under deficit and salinity stress. Measured data of first and second year were used to calibrate and validate respectively. the root mean square error (RMSE), normalized root mean square error (RMSEn), the percentage relative error and test (T-test) was used in order to comparing simulation results with measured data. Grain yield was simulated with lower the threshold 0.85 and 9% to 0.43 and 33% in the model simulation results show that Model has acceptable performance in salinities less than the threshold salinity.

Climate change (CC) is an avoidable phenomenon, which is occurring in vast parts of the world, including Iran. Agriculture and crop production are among the sectors, which are affecting from CC. Although food production activities, especially animal protein production, which have high footprints of water, have been some causes, among other important and main causes of CC occurrence. The CC moreover to increasing air temperature and hence crop water requirements, cause crop yield reduction and crop production deficiency. Therefore, considering water shortage crisis in Iran country, and in order to fulfill food security objectives of the growing population, it is necessary to coincide with the CC impacts in agriculture and to take adaptation measures and approaches in these regards. However, there are two main strategies for coinciding with CC: 1. Mitigation of CC and 2. Adaptation to CC. The mitigation strategy deals with reducing greenhouse gasses (GHG) emissions, while the adaptation strategy deals with amelioration of unavoidable impacts of CC. It includes a wide range of measures, approaches, and action selected for a vulnerable system. In this paper following an in-depth review of international and national references and policies in the field of agricultural water and food security, visions and strategies of facing with CC from the mentioned aspects are elaborated. Based on results, the following strategies and measures of adapting to CC from the agricultural water management and food security aspects could be categorized as followings: 1-Reducing water consumption during irrigation, 2-  Water conservation and reducing evaporation losses from soil surface, 3-Inceasing crop yield (increasing the numerator of water productivity index-WP), 4- Reducing the economic risk through diversity in revenue, crop insurance, subsidies and other incentives, and 5-Eetablishing early warning systems and providing training and other capacity building on the subject of adaptation to CC. However, from the strategy aspects and based on the benefit to cost ratio, in short-term the managerial measures and approaches of adaptation to CC are more efficient and less costly than the other measures, i.e. infrastructural and even agronomic measures and approaches.

Regarding the lack of water resources, the reduction of annual rainfall and the excessive growth of the population and the expansion of industry and agriculture, the use of recycled water is in fact one of the solutions to the water scarcity crisis, which is essential and inevitable. Irrigation treatments were: 1- Application of treated wastewater only 2-3times irrigation with wastewater, then use of well water 3- Irrigation with wastewater and Well water respectively 4-One irrigation with wastewater and three times with well water 5-Well water application and 6-Irrigation with well water + chemical fertilizers. The research was carried out in Austan Ghods agricultural farm in Mashhad for one year harvested. The soil texture was silty loam. The results showed that the yield of rapeseed was significantly higher in treatments that were irrigated with more treating wastewater than those treated with less treating wastewater. In fact, treatments that were irrigated with more wastewater, due to the presence of food in irrigation water, were more effective than other treatments. The amount of heavy metals, soil salinity, nitrogen percentage, absorbed phosphorus and organic matter in irrigation treatments showed a slight increase, but was not significant at 5% level. This gradual increase of the elements in the soil can be considered as a major challenge in the use of long-term refined wastewater. Opportunities from irrigation using wastewater include: tackling the problem of water scarcity, preventing pollution of the environment and surface and underground water resources, increasing the durability of high quality water resources, increasing product yield, saving on consumption expenditure chemical fertilizers and development of aquatic areas.

Agricultural crop production in greenhouses and controlled environments, due to the possibility of increasing the productivity of water and other agricultural inputs, employment creation, value-added off-season production and etc. is among the items that have been considered in the agenda of the agricultural and horticultural authorities of Iran. At the same time and as the result of decreasing in the quantity and quality of available irrigation water, issues have arisen in the established greenhouses. These conditions have led the greenhouse owners to use water desalination systems. The use of these systems is associated with the production of low quality brine, which has some problems with disposal. Therefore, the status of some greenhouses with water desalination system in Isfahan, Qazvin and Alborz provinces was studied for their saline effluent disposal. The results showed that the main alternative for brine disposal of desalination systems was unregulated land evacuation around the greenhouses and then, combined use with well water for outdoor farming, recharge of local wells and discharge into infiltrated trenches and ponds were in the following ranks. Unfortunately, due to the lack of a definite organization to control and monitor the implementation and operation of these equipments and lack of such brine disposal considerations, inappropriate situation is occurring in the surveyed areas. It seems that as the current trend continues, serious problems in means of water and soil resources contamination are not unexpected and may impose irreversible conditions on the country's environment. Therefore, this situation must be fundamentally addressed as soon as possible.

The purpose of this study was to investigate the relationship between the use of different intermittent irrigation plans with water supply satisfaction in Rasht city and the payment of water price in the period of 2000-2013. The present study is a descriptive-survey and applied purpose study. The study population consisted of paddy farmers in Rasht city and systematic sampling method. Of 78,000 water supply contractors of Sefidrood irrigation and drainage company, 384 were selected from three villages of Bijarkenar, Gorabsar and Dahanehsar in three irrigation networks (modern, semi-modern, and traditional) using Cochran formula. The data collection tool were irrigation documentation and water payment during the statistical period and a researcher-made questionnaire with 50 questions used to measure water satisfaction. Data were analyzed using descriptive and inferential statistics (Friedman test, Chi-square test, and Cramer’V coefficient). The findings of the study showed that intermittent irrigation programs in the best and worst of the water year correspond to the subjects' views with respect to the time of beginning of the period, the beginning of the shift, and the length of the water discontinuation periods. Paddy farmers' satisfaction was evaluated at the best water year at the highest level and at the worst water year at the moderate downward level. In addition, the percentage of payment of irrigation water price was the highest in the best water year and the lowest in the worst water year. According to the findings of the study, the three hypotheses of the research and the significance of the direct relationship between the research variables were confirmed. Therefore, there is a significant direct relationship between the use of different intermittent irrigation plans with water supply satisfaction and water supply in Rasht city during the period of 2000-2013.

The decline in water resources, the gradual shift of the share of water consumption in agriculture to other sectors, and the replacement of crops with higher value than strategic plants, lead to food insecurity. Inadequate water productivity and increased per capita water have resulted in the drying up of rivers, lakes and groundwater levels over time. Although groundwater extraction may be effective in producing food in the short term, it will not be sustainable in the long run. In many countries, agricultural practice in irrigated areas has become uneconomic due to the decline in groundwater level. One of the past approaches to increasing production was to increase the area under irrigated land. In the past, this was accomplished only by supplying water from groundwater sources or by controlling surface water. But it is clear that in arid and semi-arid regions such as Iran where water is scarce, this strategy, without considering proper utilization methods, will be faced new challenges such as lower water quality and soil degradation, desertification and unstable production. One of the most important strategies in addressing poverty and hunger is to make more efficient use of available water. Different solutions may be suggested to achieve this, but two major solutions must be considered in general. Increasing production by conserving existing water resources (crop management) and maintaining existing production but with less water consumption (irrigation management) are two important options to improve water productivity. One of the most effective ways to use water more efficiently is to apply pressure irrigation methods. The country's executive planners are working to increase the area of pressurized irrigation lands with the goal of making water more efficient. Due to the climatic conditions and scarcity of water resources in Iran, the development of new pressurized irrigation systems as one of the effective solutions to mitigate the critical water conditions in different parts of the country is on the serious agenda of the agricultural authorities. But surveys show that despite the development of programs and government support for the development of these methods and the paying high budgets, unfortunately the effectiveness of the systems have not been well developed. Therefore, it is necessary to investigate and identify the causes of underdevelopment as well as the growing obstacles to provide continued solutions for developing pressurized irrigation practices in the country.

Simulation of water movement in soil profile and recognition of the effect of irrigation systems on soil moisture dynamics is of great importance. For this purpose, one-dimensional LEACHW numerical model was used in selected agricultural areas of Mohammadshahr plain of Karaj. By describing 9 profiles the soil in 3 selected fields and gardens and taking into account the initial moisture conditions and monitoring their changes during the crop season or simulation period, the LEACHW model was implemented and the estimated moisture values of the model were measured with measured moisture values. The results were compared by means comparison test, sensitivity analysis of the model, and the model was again run on the basis of calibrated parameters and the amount of water lost and remaining in the soil profile during the growing season. At the output of the model, the amount of water lost and remaining in the soil profile was estimated. The results showed that modern irrigation systems were not effective in aquifer nutrition; therefore, one of the ways to increase water productivity is to reform traditional irrigation systems and move towards the development of new irrigation systems. Undoubtedly, the main task of developing new irrigation systems to ensure the country's food security is to optimize water use in the agricultural sector as the main consumer of water resources in the country.

Due to the problem of water scarcity in the country, Water supply is very important. In such circumstances wastewater reuse can be considered as one of the ways to overcome the problem of dehydration.Therefore, the use of unconventional water resources (including wastewater) in our country is becoming increasingly important. The use of such waters can provide water to the urban green space, cultivate crops that are not consumed raw and artificial nutrition for those with severe groundwater levels, a strategic policy to reduce the pressure on conventional water resources. Application of wastewater as a permanent source of water in agriculture in addition to supplying part of the water needs of this sector also saves and conserves existing water resources. In addition, the presence of plant nutrients in wastewater treatment plants reduces the use of chemical fertilizers and consequently the environmental impact of their use. In this study, considering the present population and predicting its growing trend until 2030 in Mashhad, we were able to estimate the water demand of the city. Taking into account the amount of consumption, the amount of wastewater that enters the treatment plants in the city and is discharged into the effluent was estimated. Also the volume of effluent for storage and its allocation for different purposes was estimated. According to information and surveys, it was concluded that increasing the share of water in the drinking and sanitation sector would inevitably lead to a decline in agricultural arable water. Wastewater can offset some of the decline in the share of agriculture.

Considering water productivity in different products is one of the basic parameters in optimizing the optimal use of inputs and performance. In this regard, water as one of the most important inputs should be given special attention. This study was conducted to evaluate irrigation water productivity in wheat, tobacco, watermelon and tomato as the main products of Bushehr Province. The most irrigation water productivity for these products was 0.45, 0.19, 7.73 and 12.77 kg / ha, respectively. The results showed that the use of drip irrigation system increases water productivity. In all cases, water utilization in the drip irrigation system was higher than the surface irrigation system. The drip irrigation system increased the productivity of water by 3 to 5 times, and reduced water consumption by 2 times, and increased the yield by 2 time in products such as tomato and watermelon. The failure of the drip irrigation system in the saline water resources use was due to inappropriate design and utilization, in particular the lack of proper utilization of water filtration filters. In the agricultural sector of the province, despite the existence of various deficiencies, valuable knowledge is available in the farmers of the region, especially in areas such as tomato cultivation, which can be used for these capacities.

Roughness Coefficient (RC) is one of the important and effective factors in open channel design. The precision value RC is necessary to design and utilize earth canals. Therefore, the current study was conducted to evaluate roughness coefficients in vegetated channels by Cynodon dactylon at the Moghan plain (in North-west of Iran). In the network of Morgan, 30 drainage canal sections were selected to measure water flow velocity (with a flow meter) and canal cross sections (with profilimetery devices). Results revealed that RC varied from 0.01 to 0.4 and averaged as 0.08 in vegetated canals by Cynodon dactylon. Also, flow velocity, flow section area, wetted perimeter, hydraulic radius and roughness coefficient were lognormal in distributions. Results also showed that flows were turbulent and with an increase in Reynolds numbers, roughness coefficients decrease. Sensitivity analysis of flow rate to roughness coefficient showed that with increase as 200 and 300 percent in roughness coefficients, flow rates were 0.50 and 0.33 of flow rate from average roughness coefficient. Also, with decrease 50 and 25 percent in roughness coefficients, flow rates were 2 and 4 folds of flow rate from average roughness coefficient. Thus, sensitivity of flow rate to roughness coefficient was significant and it is recommended necessary precision in the engineering estimation and computations in the selection of roughness coefficients.

Drip irrigation in greenhouses may be used as a common method, but because of the diversity of the drip irrigation systems, farmers are confused. Therefore, technical evaluation of drip irrigation system could lead to the selection of a suitable system. In this study was carried out technical evaluation of two drip irrigation systems including tape drip irrigation and drip line in strawberry greenhouse in kishestan greenhouse town located in Somesara (Guilan province). Treatments included two drip irrigation systems (tape and drip line). The result showed all of technical indexes apart of discharge pressure equation in tape drip irrigation is more than drip line and they had not statistical different. Distribution Coefficient Uniformity of the tape drip irrigation system was better than the drip irrigation systems.

So as to simulate rice yield and water use efficiency using AquaCrop and SWAP models, a research study was conducted at Khuzistan Agricultrual Research Station. In this study, three types of cultivation (D1: transplanting, D2: current directs seeding consorted seeding, and D3: dry bed seeding) and rice cultivars (V1: Red-Anbori, V2: Champa, V3: Danial) were considered. Results of MBE (0.36 ton.ha-1), RMSE (0.1.07 ton.ha-1) and NRMSE (0.14 ton.ha-1) showed that AquaCrop had good accuracy for simulation of rice yield. Mentioned statistical criteria for yield simulated by SWAP were 0.54 ton.ha-1, 1.09 ton.ha-1 and 0.15, respectively, which showed a good accuracy for this model. MBE, RMSE and NRMSE values for water use efficiency calculated by AquaCrop were -0.11 kg.m-3, 0.40 kg.m-3 and 0.15, respectively, and by AquaCrop were -0.10 kg.m-3, 0.40 kg.m-3 and 0.15, respectively. Average difference between observed and simulated yield by AquaCrop and SWAP were 0.64 ton.ha-1 and 0.67 ton.ha-1, respectively. Those values for water use efficiency were 0.02 kg.m-3 and 0.025 kg.m-3, respectively. The results revealed that both AquaCrop and SWAP had acceptable accuracy for simulation of different rice cultivars yield and water use efficiency under various cultivation types, however, AquaCrop had a bit better accuracy.