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Excessive use of nitrate fertilizers in agriculture causes harm to humans and the environment. The most suitable nitrate removal process is heterotrophic biological denitrification. The purpose of the present study was to evaluate the performance of three shapes of denitrification bioreactors: triangular, rectangular and semicircular. The main element that was used to remove nitrate was beech woodchips. The concentration of inlet nitrate was 75 mg/l and the salinity of the solution was 1 ds/m and 5 ds/m, for a period of six months. The results showed that the efficiency of the triangular bioreactor with a salinity level of 1 ds/m was 90%, which is more efficient than the rectangular and semicircular bioreactors with performances of 55.8% and 53.8%, respectively. The results also indicated that at a salinity level of 5 ds/m, the semicircular bioreactor with a performance of 50.8% inlet nitrate removal was the best of the three shapes of bioreactors tested, the efficiencies of the triangular and rectangular bioreactors were 49.9% and 48.6% respectively. Also, it was observed that at the salinity level of 1 ds/m, a high hydraulic retention time had a high positive effect on denitrification, on the other hand at the salinity level of 5 ds/m, there was better performance of denitrification if the hydraulic retention time was lower.

Photosynthesis and stomata dynamically respond to transient changes in light intensity; however, information regarding their long-term responses to the light intensity is limited. In the current study, biophysical properties of photosynthetic apparatus and stomatal characteristics of lettuce plants were investigated in response to long-term exposure to different photosynthetic photon flux densities (PPFDs) [75, 150, 300, and 600 µmol m−2 s−1]. Contrary to leaf growth, SLA decreased with increasing light intensity (i.e., thicker leaves under higher light intensity). Improving effect of higher light intensity on leaf fresh and dry weights was time dependent, in a way that the largest difference in biomass gain was observed following 40 days of exposure to the light treatments. Depending on the leaf developmental stages, exposure to higher light intensities caused faster development of photosynthesis system [in terms of improvement in the maximum quantum efficiency of photosystem II (PSII) and non-photochemical quenching (NPQ)] compared to lower light intensities. PSII performance index on an absorption basis was the highest under 600 PPFD. Small-sized stomata with narrow pore apertures were observed in plants grown under 75 PPFD; however, due to improvement in photosynthetic capacity and also the growth of the plants, water use efficiency (WUE) increased in a light intensity-dependent manner and the highest WUE was detected in 600 PPFD-exposed plants. In conclusion, exposing lettuce plants to higher light intensities (non-stress threshold levels) results in higher accumulation of biomass, faster development of photosynthetic system, and improved WUE.

The projection of climate change impacts can be very crucial for water resources planning and management. Hashtgerd plain is an immigrant destination due to socio-economic development and its proximity to the Tehran metropolis. The population growth has led to more water demand, resulting in excessive utilization of groundwater resources and water shortages in the agricultural sector. The water shortage and climate change in Hashtgerd plain could lead to more severe water crisis in the future. Therefore, this study aimed to provide adaptation strategies for minimizing the negative effects of climate change by taking into account the interaction between different sub-systems in Hashtgerd plain during 2020–2049 period. In order to assess the climate change impacts, the output of 19 AOGCMs models was used under RCP2.6, RCP4.5 and RCP8.5 emission scenarios. A comprehensive model was developed based on the system dynamics theory to investigate the interactions of water resources, agriculture, and socio-economic sub-systems and were used to investigate the impacts of climate change and evaluate various adaptation strategies on different sub-systems of the region. The simulation results showed the negative effects of climate change will intensify the water shortage in Hashtgerd Plain. The agricultural sector will be more vulnerable to climate change than the domestic and industrial sectors. The results of various policies showed that improving water use efficiency coupled with reducing the cultivation of high-consumption crops and changing the cropping pattern towards lower water requirement plants can effectively minimize the adverse impacts of climate change on water shortages in agriculture.

The accurate estimation of water productivity (WP) and plant production becomes imperative in planning and managing irrigation practices. Light intensity and CO2 concentration are among the most important determinants of growth and WP of crops. In this study, the adaptive neuro-fuzzy inference system (ANFIS) was used to model the changes in growth parameters, stomatal properties, and WP of lettuce due to various scenarios of light intensity and CO2 concentration. The lettuce plants were exposed to four levels of light intensity [75, 150, 300, and 600 µmol m−2 s−1 Photosynthetic Photon Flux Density (PPFD)] and CO2 concentration (400, 800, 1200, and 1600 ppm). The results showed that growth parameters such as fresh weight, dry weight, and leaf area improved by increasing the PPFD and CO2 concentration from 75 to 300 µmol m−2 s−1 and 400–1200 ppm, respectively. Maximum fresh weight was recorded at 300 µmol m−2 s−1 PPFD and 1600 ppm CO2 concentration while the highest dry weight was obtained at 600 µmol m−2 s−1 PPFD and 1600 ppm CO2 concentration. Stomatal pore width and length decreased by increasing PPFD and CO2 concentration. Moreover, evapotranspiration increased when plants were exposed to higher PPFDs and CO2 concentrations. ANFIS predicted all growth parameters, stomatal properties, and WP with acceptable performance (R2 > 0.99, RMSE

Sedimentation formation is a complex hydraulic phenomenon that has emerged as a major operational and maintenance consideration in modern hydraulic engineering in general and river engineering in particular. Sediments accumulation along the river course and their eventual storage in a form of islands affect water intake in the canal systems that are fed by the storage reservoirs. Without proper management, sediment transport can lead to major operational challenges in water distribution system of arid regions like the Dez and Hamidieh command areas. The paper aims to investigate sedimentation in the Western Canal of Dez Diversion Weir using the SHARC model and compare the results with the two intake structures of the Hamidieh dam in Iran using SSIIM model. The objective was to identify the factors which influence the process, check reliability of outcome and provide ways in which to mitigate the implications on operation and maintenance of the structures. Results estimated sand and silt bed loads concentrations to be 193 ppm and 827ppm respectively. This followed ,ore or less similar pattern in Hamidieh where the sediment formation impeded water intake in the canal system. Given the available data on average annual bed loads and average suspended sediment loads of 165ppm and 837ppm in the Dez, there was a significant statistical difference (16%) between the sand grains, whereas no significant difference (1.2%) was find in the silt grain sizes. One explanation for such finding being that along the 6 Km river course there was considerable meandering effects which explains recent shift in the hydraulic behavior along the stream course under investigation. The sand concentration in downstream relative to present state of the canal showed a steep descending curve. Sediment trapping on the other hand indicated a steep ascending curve. These occurred because the diversion weir was not considered in the simulation model. The comparative study showed very close similarities in the results which explains the fact that both software can be used as accurate and reliable analytical tools for simulation of the sedimentation in hydraulic engineering.