Maximum Water Productivity Research Articles

Water Requirements, Soil Moisture Availability, and Their Effects on Quinoa (Chenopodium quinoa Willd.) Development and Yield

Throughout the world, about 70% of the total water is used for irrigation. Reports show that there will be a significant increase in irrigation requirements, as irrigation is an important factor affecting water footprint and productivity worldwide [45]. The experiment described in this article was carried out at the Agricultural Research Station, Ministry of Agriculture, Iraq, in 10 kg pots to evaluate the effects of soil moisture availability on water requirements, water productivity, and quinoa crop productivity under different irrigation treatments. These treatments maintained the soil at different levels of soil water tension (-0.05, -0.10, -0.15, -0.30, and -0.40 MPa) during the vegetative and/or reproductive periods of growth. The study analyzed water consumption, plant growth, yield components, and water productivity of the quinoa crop. The data showed that evapotranspiration decreased with increasing soil moisture tension during both the vegetative and reproductive periods of development. The maximum water productivity was consistently recorded at the lowest soil moisture tension, highlighting moisture efficiency. It was concluded that quinoa is relatively tolerant to soil moisture stress during the vegetative period compared to the reproductive period. The number of grains per ear was identified as a limiting factor for grain yield.

Improving yield and irrigation water productivity of green beans under water stress with agricultural solid waste-based material of compacted rice straw as a sustainable organic soil mulch

AbstractThis research aimed at water saving in irrigation by applying deficit irrigation using two strategies, standard drip and partial root drying (PRD), while applying organic and plastic mulch over two growing seasons of green beans. A field experiment was conducted in 2022 and 2023, using four irrigation treatments supplying 100% of the irrigation requirement (IRg), 75% IRg, 50% IRg, and 50% IRg—PRD, and four soil mulching treatments: uncovered soil (UC), plastic mulch (PM), rice straw mulch (RSM), and compacted rice straw mulch (CRSM). The combined effect of deficit irrigation strategies and soil mulching showed that the maximum irrigation water productivity (IWP) of 5.56 kg m−3 was achieved under 50% IRg—PRD & CRSM for both growing seasons, followed by 50% IRg—PRD & RSM and 50% IRg—PRD & PM, with 5.19 and 4.96 kg m−3, respectively. The highest yield of 8936 kg ha−1 was achieved with 50% IRg—PRD & CRSM, followed by 8914 kg ha−1 and 8898 kg ha−1 with 100% IRg & CRSM and 75% IRg & CRSM, respectively. The lowest yield of 6009 kg ha−1 was obtained with 50% IRg & UC. The highest soil moisture content was observed under 100% IRg & CRSM. The application of organic mulches was found to be particularly effective in conserving soil moisture due to enhanced infiltration, improved retention capacity, and suppression of weed growth, ultimately fostering optimal crop development and higher yield. The results of soil temperature variations beneath soil mulches showed that CRSM is effective in alleviating plant water stress, lowering the temperature below the cover and reducing water loss through evaporation from the soil surface. The combination of 50% IRg—PRD & CRSM produced plants with enhanced plant height, fresh and dry weight, leaf area, pod length, and green bean weight, as well as the highest vegetative growth indices. Generally, the organic mulching increased soil temperature, soil moisture, IWP, and green bean production.

Drip Irrigation of Tomatoes in Biskra: Water Saving and Economic Profitability

A field survey of thirty tomato growing greenhouses in Biskara region of Algeria was undertaken to find out the kind of the irrigation method being used and to assess their water productivity and economics. 30% of the greenhouses employed drip irrigation (9 farms), 20% (6 farms) utilized furrow irrigation, while the rest used the mixed irrigation. The sowing/transplantation of tomato in greenhouses in the region was carried out from August to October. The production started from March and ended in June. The selling price per kilogram of tomatoes ranged between 25 and 105 Algerian Dinar (DA). Results revealed that greenhouses using drip irrigation had higher water productivity and lower total water requirements. Greenhouses using drip irrigation produced 71.7 tons tomatoes ha-1, which is 33.7% higher than that using furrow irrigation. Drip irrigated greenhouses exhibited maximum water productivity of 20.4 kg m3. Total water consumption in the greenhouses using drip was 3722.2 m3 ha-1 while it was 10248 m3 ha-1 in the furrow irrigated. Average financial returns from the drip irrigated greenhouses were about 36% higher than farms using furrow irrigation.

Analysis of the Status of Irrigation Management in North Carolina

Farmers in North Carolina are turning to irrigation to reduce the impacts of droughts and rainfall variability on agricultural production. Droughts, rainfall variability, and the increasing demand for food, feed, fiber, and fuel necessitate the urgent need to provide North Carolina farmers with tools to improve irrigation management and maximize water productivity. This is only possible by understanding the current status of irrigated agriculture in the state and investigating its potential weaknesses and opportunities. Thus, the objective of this study was to perform a comprehensive analysis of the current state of irrigation management in North Carolina based on 15-year data from the Irrigation and Water Management Survey by the United States Department of Agriculture–National Agricultural Statistics Service (USDA-NASS). The results indicated a reduction in irrigation acres in the state. Also, most farms in the state have shifted to efficient sprinkler irrigation systems from gravity-fed surface irrigation systems. However, many farms in North Carolina still rely on traditional irrigation scheduling methods, such as examining crop conditions and the feel of soil in deciding when to irrigate. Hence, there are opportunities for enhancing the adoption of advanced technologies like soil moisture sensors and weather data to optimize irrigation schedules for improving water efficiency and crop production. Precision techniques and data-based solutions empower farmers to make informed, real-time decisions, optimizing water use and resource allocation to match the changing environmental conditions. The insights from this study provide valuable information for policymakers, extension services, and farmers to make informed decisions to optimize agricultural productivity and conserve water resources.

Impacts of Adding Porous Media and Phase Change Material on Performance of Solar Water Distiller System Under Iraq Climatic Condition: An Experimental Study

ABSTRACTThis current investigation involves an experimental inspection of adding porous medium and phase change material (PCM) above the absorber surface to enhance the performance of a single slope and single basin solar water distiller system. To demonstrate the effectiveness of adding porous medium and PCM, the performance of the modified system and conventional system is compared under similar operating conditions. The system that uses porous medium and PCM is called MSS‐FPP, whereas the conventional system is called MSS‐F. Rectangular fins are fixed above the absorber plate for both models. For MSS‐FPP model, three different types of porous medium (stones, nuts, and black glass balls) are used in addition to paraffin wax filled inside circular tubes as a PCM. The data are collected in November and December 2023 in Mosul City, Iraq. The experiments are carried out under different water depths. The findings confirm that the performance of MSS‐FPP model is better than MSS‐F model by 41.32% (for water depth 3 cm) and 30.61% (for water depth 5 cm). The results also indicated that the water productivity of MSS‐FPP model is higher than MSS‐F model by 41.67% (for water depth 3 cm) and 30.65% (for water depth 5 cm). For MSS‐FPP model, the maximum water productivity and efficiency are obtained when using black glass balls as compared to nuts and stones types, where the highest water temperature and water productivity values are found equal 54°C and 1.01 kg/m2 for water depth 3 cm. The enhancement in the performance of modified solar water distiller system (MSS‐FPP) shows that using a porous medium and PCM has considerable impacts on the evaporation rate, heat exchange, and rate of heat transfer.

Impact of drip irrigation and plastic mulching on yield and economics of cucumber (Cucumis sativus L.)

Drip irrigation is crucial in the current agricultural scenario for vegetable crops, as it optimizes water use efficiency by delivering precise amounts of water directly to the plant roots, thereby conserving water resources and enhancing crop yields. Yield enhancement in cucumber, a significant horticultural crop, can be achieved by integrating drip irrigation and plastic mulching to maximize water productivity while minimizing losses. In the current consequences, a field study was conducted from November to December in two consecutive years (2021-2022 and 2022-23) at the experimental field of Precision Farming Development Centre, Indian Institute of Technology, Kharagpur, India. The study aimed to quantify the irrigation water requirements for cucumber using drip irrigation and plastic mulch. Eight treatments with varying irrigation levels and the use of plastic mulch were assessed in a randomized block design with three replications. The crop's irrigation water requirement was determined using the FAO-56 Penman-Monteith model. The results showed that the highest plant height (193.5 cm), number of leaves (43.3), fruit length (18.5), fruit weight (279.0 g), and cucumber yield (15.9 t/ha) were achieved with 100% irrigation water requirement along with plastic mulch during the first and second season. These results were closely followed by treatments with 80% of the crop water requirement using drip irrigation and plastic mulch. The study concluded that applying 80% of the estimated irrigation water (142.1 mm) using drip irrigation and plastic mulch could be recommended to obtain higher productivity in cucumber.

Water Productivity of Mustard Green (Brassica juncea L.) with Variation of Irrigation Systems

Drip irrigation and self-watering are two examples of irrigation technology improvements that employ effective and efficient watering methods. Water productivity may be used as a benchmark to compare irrigation efficiency and agricultural productivity. The purpose of this study was to assess mustard green's water productivity under conventional, drip, and self-watering irrigation systems. The effect of irrigation variation on mustard green growth was studied using a nonfactorial technique with a completely randomized design (CRD). The design has three treatments and six replications. This study examined the following variables: height, number of leaves, yield, irrigation water utilized, and water productivity of mustard green. The study found that mustard green plants require 0.69 mm/day of water in the vegetative phase, 2.83 mm/day in the generative phase, and 1.69 mm/day in the final phase. The use of different watering systems has a significant influence on mustard green's height and leaf number. Self-watering at 15 g/L provides the maximum water productivity for mustard green, followed by drip irrigation at 8.46 g/L and conventional irrigation at 7.69 g/L. Keywords: Drip irrigation, Mustard green, Self-watering irrigation, Water productivity

Response of Malt Barley (<i>Hordeum distichum L.</i>) to Different Phosphorus Fertilizer Rates and Irrigation Levels Under Furrow Irrigation Methods in South Eastern Ethiopia

Nutrient availability to crops is a function of soil type, moisture condition, environment, crop type, and management and their interaction affects nutrient use efficiencies and crop growth conditions. The objective of this study was to determine the optimum P rate and deficit irrigation level, as well as to identify the interactive effect of nutrient and moisture levels on yield and yield quality malt barley under irrigation in Ormiya region Tiyo district. The experiment was conducted at small plot level for three consecutive years from 2020/21 to 2022/23 G.C. This experiment was conducted at Kulumsa Agricultural Research Center On-Station arranged by split-plot layout with RCBD design by three replications. Irrigation amounts (100%, 75% and 50%) were assigned the main plot and phosphorus fertilizer rates (0, 10, 20, 30 and 40 kg) corresponded to the subplot. The combined effect of irrigation levels and phosphorus fertilizer rate had a significant effect (p < 0.05) on malt barely grain yield, above-ground biomass, thousand kernel weight and water productivity but not on plant height, seeds per spike and protein content. The highest grain yield and above-ground biomass were 3.16 t/ha and 6.77 t/ha obtained from the application of 100% ETc with 30 kg of phosphorus fertilizer. The maximum water productivity (0.97 kg/m<sup>3</sup>) was observeat the application of 75% ETc with 30 kg of Phosphorus fertilizer while more profitable practice was found at 100% ETc with 30 kg of phosphorus application. The highest protein content (15.57%) was observed at the application of 50% deficit irrigation and the lowest (14.66%) was observed at 100% ETc irrigation application. Applying the optimum amount of irrigation with 30 Kg phosphorus fertilizer gives high grain and above biomass yield and is economically profitable in Tiyo district and agroecologies similar to Tiyo.

Retraction: Water Supply 23 (3), 1362–1374: Integrated modeling of food–water–energy nexus for maximizing water productivity, Majid Khayatnezhad, Ebrahim Fataei and Aliakbar Imani

Retraction: <i>Water Supply</i> 23 (3), 1362–1374: Integrated modeling of food–water–energy nexus for maximizing water productivity, Majid Khayatnezhad, Ebrahim Fataei and Aliakbar Imani

Expression of Concern: Water Supply 23 (3), 1362–1374: Integrated modeling of food–water–energy nexus for maximizing water productivity, Majid Khayatnezhad, Ebrahim Fataei and Aliakbar Imani, https://dx.doi.org/10.2166/ws.2023.038

Expression of Concern: <i>Water Supply</i> 23 (3), 1362–1374: Integrated modeling of food–water–energy nexus for maximizing water productivity, Majid Khayatnezhad, Ebrahim Fataei and Aliakbar Imani, https://dx.doi.org/10.2166/ws.2023.038

Evaluation of water management effects on potato yield and water productivity in northeast Iran using the SWAP model

ABSTRACT The agro-hydrological SWAP model was employed for simulation of evapotranspiration, yield, and water productivity of potato under six irrigation scenarios (100, 90, 80, 70, 60, and 50% potato water requirement (WR)) in Fariman, Ghoochan, and Golmakan in the northeast Iran. The results showed that the SWAP model well-simulated potato yield and water productivity. The model slightly overestimates the potato yield and underestimates the water productivity. The results revealed that irrigation scheduling is an important factor effecting on evapotranspiration, yield, and water productivity of potatoes. By decreasing irrigation water to 50% WR, potato evapotranspiration and yield decreased in all three study areas. However, potato water productivity increased in Fariman and Golmakan and decreased in Ghoochan, as irrigation volume decreased to 50% WR. In Fariman and Golmakan, irrigation at the rate of 80% WR led to the best irrigation management to have maximum water productivity (2.96 and 2.48 kg m−3, respectively) and acceptable potato yield (21,376.2 and 10,998.7 kg ha−1). In Ghoochan, by adopting the irrigation scenario at the level of 90% WR, the potato yield decreased by approximately 7.6% compared to the full irrigation conditions. However, the highest amount of water productivity (2.27 kg m−3) was achieved.

Effects of irrigation and fertilization with biochar on the growth, yield, and water/nitrogen use of maize on the Guanzhong Plain, China

Excessive water and nitrogen inputs in agricultural production can result in resource wastage and environmental pollution. This makes it imperative to identify effective farmland management strategies to ensure sustainable agriculture development, and it remains to be explored whether biochar can be an effective solution. In this study, a 2-year (2021 and 2022) field experiment was conducted with two irrigation levels, W100 (ET) and W80 (0.8 ET), and three nitrogen fertilizer levels, NH (270 kg ha−1), NM (180 kg ha−1), and NL (90 kg ha−1), in full combination with biochar (30 t ha−1). The NM and N0 treatments without biochar at both irrigation levels were set as controls. The results of the study showed that there was no significant difference in maize yield between the high and medium N treatments. Further, maximum water productivity (WP), nitrogen agronomic efficiency (NAE), and nitrogen recovery efficiency (NRE) were obtained in NM treatments when water and nitrogen were kept consistent. Deficit irrigation was effective in reducing water consumption and increased WP by 15.54% and 11.06% in 2021 and 2022, respectively. Biochar application increased WP, nitrogen use efficiencies, and significantly increased the yield by 7.02% and 6.46% in 2021 and 2022, respectively. Therefore, the application of biochar can be an effective measure to promote crop growth and resource use. Based on the results of this experiment, an irrigation level of 0.8 ET in combination with NM and biochar application is recommended to ensure the sustainability of agricultural production.

Effect of different soil moisture regimes on yield and water use efficiency of groundnut at Kobo irrigation scheme, Kobo Ethiopia

In the arid and semi-arid part of Eastern Amhara, water is the most important yield-limiting factor for agricultural production. Application of the right amount of irrigation water at a right time helps to optimize water loss and increases crop yield. Therefore, a field experiment was conducted at Kobo irrigation scheme to determine the optimal crop water requirement and irrigation frequency for yield and water use efficiency of groundnut. The CROPWAT model could generate the 100% irrigation scheduling as 40 mm irrigation water with 8 days. Field base validation and ground truthing is vital. Therefore, the treatments were formulated by the factorial combinations of the three crop water levels as 75% ETc (30 mm), 100% ETc (40 mm), 125% ETc (50 mm) with three irrigation intervals (6 days, 8 days and 10 days). The treatments arranged in randomized complete block design with three replications. The statistical analysis was carried out using Genstat 15.0 software and the mean comparison was done using least significant difference (LSD) test. The analysis revealed that the crop water use efficiency was significantly (p&lt;0.05) affected by the main effects of crop water levels, irrigation interval and by their interaction, whereas the grain yield does not show a significant (p&gt;0.05) response. As the water levels declined and the irrigation intervals varied, the grain yield tends a fairly constant trend. However, based on the commerciality of the crop, application 75% ETc (30 mm) with 8 days irrigation interval gave numerically maximum grain yield of 3466.9 kg/ha and it has nearly more than 200 kg relative yield advantage over most treatments. The highest water use efficiency (0.9 kg/m3) was recorded from the combination 75% ETc (30 mm) with 10 days; while it was statistically at par with 75% ETc with 8 days interval (0.8 kg/m3) applied treatment. From the result, it could be concluded that the maximum yield and maximum water productivity were simultaneously achieved by combined application of 75% ETc with 8 days interval and saves 4600 m3 water to irrigate an additional 1.2 ha compared with 125% (50 mm) ETc with 6 days interval applied treatment.

Effect of Deficit Irrigation on Maize (Zea Mays L.) Crop Under Conventional, Fixed, and Alternate Furrow Irrigation for Effective Irrigation Water Management

A study was conducted with the objective of determining the effect of deficit irrigation on maize (Zea mays L.) under conventional, fixed, and alternate furrow irrigation. The experiment was conducted at Jimma Agricultural Research Center (JARC) in 2014/2015 and 2015/2016 dry periods. Nine treatments of different deficit irrigation levels were factorial combined and randomized in plots, and all cultural practices were done. The crop water requirement was calculated using the CROPWAT8.0 program. Yield and growth parameter data were recorded, and analyzed using SAS software. The two-year over-all statistical analysis result showed that, different deficit irrigation levels had a significant effect (p&lt;0.05) on grain yield, ear height, fresh biomass, 100 seed weight, girth, and water productivity. However, there was no significant effect (p &gt; 0.05) on plant height and internode length. The result revealed that 100% ETc conventional furrow gave the highest grain yield (106.1 Qun/ha), followed by 75% ETc conventional furrow (101.23 Qun/ha) and 50% ETc conventional furrow (81.86 Qun/ha). The minimum yield of 55.64 Qun/ha was obtained at a fixed 50% furrow irrigation, and there was a 52.44% yield improvement. The maximum fresh biomass of 196.5 Qun/ha was obtained from 100% conventional furrow, and the minimum 103.40 Qun/ha was at 50% fixed furrow irrigation. The maximum and minimum water productivity of 8.007 and 2.8 kg/m3 were obtained at 75% conventional and 100% fixed furrow irrigation, respectively. Considering the water productivity, net economic benefit and sustainable production of the crop in the agroecology of the study area, combination of 55% up to 85% of deficit irrigation level with conventional furrow irrigation system could be recommended for the production of maize in a deficit furrow irrigation method. Based on the observations made and the statistical analysis done, fixed furrow irrigation was not recommended for the study area.

Crop acreage planning for economy- resource- efficiency coordination: Grey information entropy based uncertain model

Reasonable adjustment of crop acreage can improve the sustainability of agriculture in arid zones by promoting economic development, alleviating water scarcity, and improving resource utilization efficiency but meets the challenges of various decision-maker preferences and uncertainties. With the objectives of maximizing economic benefits, minimizing evapotranspiration, and maximizing water productivity and water production efficiency, this study developed a grey entropy based multi-objective fuzzy constraint interval programming model (GEMOFCIP) through incorporation of information entropy technology, fuzzy constraints and interval programming approaches within a general optimization framework. The model is capable of (1) generating the crop acreage management schemes through trading off the different development goals; (2) dealing with the structure and parameter uncertainties of the optimization model; (3) measuring the relative importance of multiple objectives by the introduction of information entropy with the insufficient decision-maker’s preference information. Taking the crop acreage planning problem in Liangzhou, northwest China as a case study, the model was solved under different water-saving and satisfaction degree scenarios. It turned out that, after optimization, the economic benefit, water productivity and water production efficiency have been significantly improved, while the total ET and the total irrigation water have been significantly compressed in the study area. The GEMOFCIP model is superior to the previous models in that it takes into account the randomness of the relative importance of system objective, the vagueness of system constraints and the fluctuations of system coefficients, which would make the model more reasonable, stable and objective. Optimal results can help manage crop pattern with the economy-resource-efficiency consideration and accelerate the healthy development of agriculture in arid zones.

Diagnosing crop water status based on canopy temperature as a function of film mulching and deficit irrigation

Film mulching with deficit irrigation is considered an effective way to maximize water productivity and ensure a stable crop yield in the arid region of Northwest China. Deficit irrigation requires precise knowledge of crop response to drought conditions, whereas the canopy temperature and the related crop water stress index (CWSI) monitor crop water stress status. Although canopy temperature and CWSI are closely related to meteorological conditions, cultivation measure and crop growing conditions, it is unclear how film mulching influences the canopy temperature and CWSI. A two-year field experiment was conducted in a maize field with three irrigation levels and different film mulching conditions, i.e., non-mulching, plastic film mulching and biodegradable film mulching treatments, in the Shiyang River Basin of Northwest China. The study aimed to quantify the effects of film mulching on canopy temperature and CWSI, as well as to compare CWSI values obtained from the nearby meteorological station data (CWSI_M), and in situ (field) measurements (CWSI_I). The results showed that plastic film and biodegradable film significantly (p < 0.05) reduced the canopy temperature. The non-water-stressed baseline based on the air temperature and relative humidity of the nearby meteorological station was significantly (p < 0.05) different from those of the field measurement at both the vegetative and the reproductive stages. No significant differences in the non-water-stressed baselines (p > 0.05) were observed among different film mulching conditions. CWSI was calculated using the air temperature and relative humidity data from the aforementioned two sources. The results revealed showing that CWSI_I better correlated with the crop yields of various treatments when compared to CWSI_M. Irrigation scheduling based on CWSI_I could save 83 mm of irrigation amount. This underscore the preference of using CWSI_I (if available) as the primary choice for irrigation scheduling. These findings highlight the impact of meteorological and planting conditions on the canopy temperature, non-water-stressed baseline and CWSI, which may be valuable for diagnosing crop water status more accurately by regional water managers.

Threshold Values of Plant Water Status for Scheduling Deficit Irrigation in Early Apricot Trees

Irrigated agriculture is facing a serious problem of water scarcity, which could be mitigated by optimizing the application of regulated deficit irrigation (RDI) strategies. For this reason, the aim of our study was to determine irrigation thresholds based on direct water status indicators of apricot trees under RDI to maximize water productivity. Three treatments were tested: (i) Control (CTL), irrigated at 100% of the crop evapotranspiration (ETc) during the entire crop cycle; (ii) RDI1, irrigated as CTL, except during fruit growth stages I–II when irrigation was reduced by 20% of CTL, and during late post-harvest, with an irrigation threshold of a moderate water stress of −1.5 MPa of stem water potential (Ψs); and (iii) RDI2, irrigated as RDI1, but during late post-harvest using a severe water stress threshold of −2.0 MPa of Ψs. As the irrigation scheduling of RDI1 and RDI2 did not affect yield and fruit quality, the crop water productivity was increased by 13.2 and 25.6%, respectively. This corresponded to 1124 and 2133 m3 ha−1 of water saved for RDI1 and RDI2. A water stress integral of 30.2 MPa day during post-harvest could be considered optimal since when 41 MPa day was accumulated, vegetative growth was reduced by 35%. The non-sensitive periods to water deficit were delimited by the accumulation of growing degree days (GDD) from full bloom, the end of fruit growth stages I–II corresponded to an accumulation of 640 °C GDD, and the beginning of the late post-harvest to an accumulation of 1840 °C GDD.

Dewatering of Scenedesmus obliquus Cultivation Substrate with Microfiltration: Potential and Challenges for Water Reuse and Effective Harvesting

In the microalgae harvesting process, which includes a step for dewatering the algal suspension, directly reusing extracted water in situ would decrease the freshwater footprint of cultivation systems. Among various algae harvesting techniques, membrane-based filtration has shown numerous advantages. This study evaluated the reuse of permeate streams derived from Scenedesmus obliquus (S. obliquus) biomass filtration under bench-scale and pilot-scale conditions. In particular, this study identified a series of challenges and mechanisms that influence the water reuse potential and the robustness of the membrane harvesting system. In a preliminary phase of this investigation, the health status of the initial biomass was found to have important implications for the harvesting performance and quality of the permeate stream to be reused; healthy biomass ensured better dewatering performance (i.e., higher water fluxes) and higher quality of the permeate water streams. A series of bench-scale filtration experiments with different combinations of cross-flow velocity and pressure values were performed to identify the operative conditions that would maximize water productivity. The selected conditions, 2.4 m·s−1 and 1.4 bar (1 bar = 105 Pa), respectively, were then applied to drive pilot-scale microfiltration tests to reuse the collected permeate as a new cultivation medium for S. obliquus growth in a pilot-scale photobioreactor. The investigation revealed key differences between the behavior of the membrane systems at the two scales (bench and pilot). It indicated the potential for beneficial reuse of the permeate stream as the pilot-scale experiments ensured high harvesting performance and growth rates of biomass in permeate water that were highly similar to those recorded in the ideal cultivation medium. Finally, different nutrient reintegration protocols were investigated, revealing that both macro- and micro-nutrient levels are critical for the success of the reuse approach.

Performance evaluation of a novel humidification-dehumidification desalination system operated by a heat pump

Decentralized and small-scale desalination technologies can effectively address the limitations associated with large-scale desalination systems and contribute to solving the issue of fresh water scarcity. However, low energy efficiency remains a primary obstacle in their widespread application. To tackle this challenge, this paper introduces a novel heat pump humidification-dehumidification desalination system, in which humid air from the dehumidifier enters the heat regenerator and heat pump evaporator in sequence, enabling deep dehumidification. Subsequently, the cold air is reheated by the heat regenerator and subcooler before entering the humidifier. This sequential process can increase not only the energy efficiency of heat pump but also the fresh water productivity. Models are proposed and calculated for the theoretical evaluation of the novel system. Firstly, heat pump design parameters are optimized. Subsequently, performances of the novel system under different operation conditions are compared with those of the conventional system. The results indicate that optimizing heat pump system design parameters can significantly improve system performance. When compared to the conventional system, the novel system exhibits significant improvements. It achieves a maximum fresh water productivity of 39.73kg/h, representing an increase of 12.83%, and a maximum gain output ratio of 6.52, which is 13.39% higher. The lowest fresh water production cost is 9.52 $/m3, also a reduction of 5.15%. Additionally, both the novel and conventional systems possess optimal feed temperature and mass flow rate ratio. At last, the optimal performances of the novel system are compared with the reported results, which further validates the thermodynamic and economic advantages of the novel system.

Adaptation to seasonal drought in irrigation districts of south China: A copula-based fuzzy-flexible stochastic multi-objective approach for precise irrigation planning

The occurrence of seasonal drought has led to periodic water shortages in irrigation districts of south China, posing significant agricultural challenges on water and food security. Consequently, there is a pressing need for high-efficient water resources management from a sustainability perspective. To address this issue, a copula-based fuzzy-flexible stochastic multi-objective programming (CFSMP) model was proposed to facilitate irrigation planning under the combined influence of seasonal dry and wet conditions. The model was aimed to simultaneously achieve maximum economic benefit, water productivity and green water use efficiency, considering the economic, social, and environmental spheres of the irrigation district. The CFSMP model represented an innovative solution that was capable of (1) precisely describing the response of crop yield to water supply at ten-day time scale, which can be matched with practical irrigation demand; (2) characterizing joint distributions of seasonal dry and wet conditions of precipitation during different crop growth periods based on the copula function; (3) reconciling conflicts on objectives among economic, social, and environmental spheres of the irrigation district in complex and uncertain environments. The proposed model was applied to the Dongfeng Reservoir Irrigation District in south China. The downscaled ten-day Jensen water production functions of main grain and cash crops were fitted to recognize precise distributions of crop water demand and water sensitivity index. The Frank copula, with the smallest value of squared Euclidean distribution, was selected to describe the joint distribution of seasonal precipitation and gain insights into actual seasonal water availability and water scarcity. The results showed that the proposed model produced more water-saving and yield-promoting irrigation planning policies than the current quota. The average water allocation of rice, wheat, maize, rape, and citrus decreased by 352.6 mm, 10.6 mm, 67.7 mm, 7.44 mm, and 54.6 mm, respectively. Except for a yield reduction of 8.8% for rape, crop yields of rice, wheat, maize, and citrus were improved by 33.3%, 45.4%, 29.9%, and 12.3%, respectively. The coordination degree of the model reached 0.827, demonstrating excellent performance on generating coordinated and robust solutions. Therefore, the CSFMP model has the potential to alleviate seasonal drought in south China and can be applied in similar regions with comparable resources crisis.