Low Water Yield Research Articles

An All-Passive and Macropatterned Architecture Design for Water Harvesting.

Solar evaporation designs show great promise in water harvesting without electricity inputs. Unfortunately, they have been heavily limited by a low water yield. To overcome this challenge, we introduced a new architecture featuring both system-level and materials-level designs. At the system level, we implemented a macropatterned architecture with a decoupled design for water evaporation and condensation to enhance water yield efficiency. This design also ensures that condensed water droplets do not block the solar evaporation process. At the materials level, solar selective heating and radiative cooling were applied to improve passive water yield performance. As a proof of concept, our design showed an indoor water collection rate of 2.06 kg m-2 h-1 under one sun and an average outdoor water collection rate of 1.85 kg m-2 h-1 over five consecutive days. The decoupled, all-passive, and macropatterned architecture offers substantial potential for commercial water collection applications toward mitigating global water scarcity.

Balancing Water Yield and Water Use Efficiency Between Planted and Natural Forests: A Global Analysis.

Climate warming is projected to affect hydrological cycle in forest ecosystems and makes the forest-water relationship more controversial. Currently, planted forests are gaining more public attention due to their role in carbon sequestration and wood production relative to natural forests. However, little is known about how the global patterns and drivers of water yield and water-use efficiency (WUE) differ between planted and natural forests. Here, we conduct a global analysis to compare water yield and WUE in planted and natural forests using 946 observations from 112 published studies. The results showed that global average water yield coefficient was 0.29 for planted forests and 0.34 for natural forests. Planted forests exhibited lower water yield coefficient (p < 0.05) in three climatic regions (arid, dry subhumid, and humid regions), but higher (p < 0.01) WUE only in arid region, compared with natural forests. Both water yield coefficient and WUE in planted forests were significantly lower (p < 0.05) than that in natural forests for stand characteristic groups (stand density, average tree height, leaf area index [LAI], and basal area). Additionally, stand density within the ranging between 1000 to 2000 stem ha-1 can maximize the water yield and WUE in planted and natural forests. Water yield coefficient in planted forests was primarily controlled by the factors related to tree growth (i.e., tree height, DBH), while that of natural forest mainly affected by stand structure (i.e., LAI, stand density, DBH). WUE in planted forest was more sensitive to climate than in natural forests. This work highlights the critical role of natural forests in water supply and the importance of tree species selection and stand management (e.g., stand density adjustment) in plantations in future forest restoration policies and climate change mitigation.

Do Experimental Forests and Ranges of the Southeastern United States Represent the Climate, Ecosystem Structure, and Ecosystem Functions of the Region?

Abstract There are twenty experimental forest and range sites (EFRs) across the southeastern United States that are currently maintained by the USDA Forest Service (Forest Service) to conduct forest ecosystem research for addressing ecosystem management challenges. The overall objective of this study was to use multiple gridded datasets to assess the extent to which the twenty EFRs represent the climate, ecosystem structure, and ecosystem functions of southeastern forests. The EFRs represent the large variability of climate conditions across the region relatively well, but we identified small representation gaps. The representativeness of ecosystem structure by these EFRs can be improved by establishing EFRs in forests with relatively low tree cover, leaf area index, or tree canopy height. The current EFRs also represent the forest ecosystem functions of the region relatively well, although areas with intermediate and low aboveground biomass and water yield are not well represented. The trends in climate, ecosystem structure, and ecosystem functions were generally consistent between the region and the EFRs. Our study indicates that the current EFRs represent the region relatively well, but establishing additional EFRs in specific areas within the region could help more completely assess how southeastern forests respond to climate change, disturbance, and management practices. Study Implications This study across the experimental forests and ranges (EFRs) and the southeastern forest region fills the knowledge gap regarding climate, ecosystem structure, and ecosystem functions of EFRs in the context of the broader southeastern forest region. Understanding ecosystem functions and structures across the EFR network can help the Southern Research Station to address new research questions. Our study indicates that the current EFRs represent the climate, ecosystem structure, and ecosystem functions of southeastern forests well. However, establishing additional EFRs in certain regions could help more completely assess how southeastern forests respond to climate change, disturbance, and management practices.

Application Research of Integrated Geophysical Methods in Hydrogeological Survey in Extremely Arid Desert Areas

The research area is located in the Wuyi Mountain area of Dunhuang, Gansu Province, belonging to an extremely arid desert region. Previous hydrogeological surveys in the area had not conducted geophysical exploration work, and most of the hydrological boreholes previously drilled had either low water yield or almost no water yield. In this study, based on a comprehensive analysis of existing regional geological and hydrogeological data, the researchers conducted Controlled Source Audio-frequency Magnetotellurics (CSAMT) measurements and high-density electrical resistivity tomography (ERT) measurements. This work essentially identified the hydrogeological characteristics such as buried fracture water in the structural zones of the research area and water-rich properties. Hydrogeological boreholes were then deployed, and subsequent drilling confirmed a relatively high water yield.

Enhancing solar-driven atmospheric water harvesting by a bilayer macroporous hydrogel

The adsorption-based atmospheric water harvesting technique has shown great potential in providing clean water. An ideal device for atmospheric water harvesting should enable the massive and quick release of water after it is rapidly absorbed by the moisture adsorbent. At present, however, the moisture adsorbent still experiences issues such as a slow water absorption rate, hampered adsorption–desorption kinetics, and a low total water yield. In this paper, a bilayer moisture adsorbent (BMA), which glues a hydrophilic macroporous layer for rapid water adsorption and a carbonized sunlight-absorbing layer for both water harvesting and desorption acceleration, is introduced. Further evidence suggests that it is the stable, fluffy, and rough porous structure of the BMA that helps to harvest atmospheric water efficiently. The fully carbonized BMA exhibits a water absorption capacity of up to 396% at a relative humidity of 90%, which is 20% higher than a monolayer sample. More importantly, the desorption efficiency of the half-carbonized BMA reaches 98% under 1 sun illumination. These results jointly demonstrate that the BMA can play the dual role of absorbing moisture and light, allowing for rapid atmospheric water harvesting, massive water storage, and efficient desorption under the light.

Factor analysis of hydrologic services in water-controlled grassland ecosystems by InVEST model and geodetector.

Water conservation is highly important for a successful desert grassland ecosystem, but there was no comprehensive view on how to assess influencing factors in managing and addressing water yield and water conservation in desert steppe. The Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model, which is specifically used for the assessment of ecosystem services, was combined with geographic detectors to identify the priority areas for water conservation function and analyze the driving factors of water conservation in the Tabu River Basin, Inner Mongolia Autonomous Region, China, using different meteorological data sources. (i) The InVEST model has the advantage of modeling water yield and water conservation at spatial scales by fusion downscaling data. High water yield mainly occurs in the southern hilly mountainous areas, low water yield in the northern desert and grassland areas, and between the two in the central agro-pastoral areas; the multi-year average water conservation and water yield based on the InVEST model are 3.3 and 16mm, respectively. (ii) Water yield and water conservation roughly show a transitional phenomenon of "high in the south and low in the north." The water yield and water conservation per unit area of the Tabu River Basin are relatively large for construction land, unused land, and cropland, relatively small for grassland and forestland, and basically zero for water bodies. Forest land has the strongest water conservation capacity, followed by grassland and farmland, while the order of water yield capacity is the opposite. (iii) Precipitation shows the strongest explanatory power for water yield (q = 0.427), followed by land use types (q = 0.411). The precipitation ∩ actual evapotranspiration has the strongest explanatory power for water yield (q = 0.87). The explanatory power of water yield on water conservation is the strongest (q = 0.752), followed by precipitation (q = 0.4), and the water yield ∩ soil has the greatest explanatory power on water conservation (q = 0.91). These findings are crucial for promoting regional hydrologic services and can provide a water resources management strategy for decision-makers.

Analysis of effects of vegetation cover and elevation on water yield in an alpine basin of the Qilian Mountains in Northwest China by integrating the WRF-Hydro and Budyko framework

Alpine basins provide the main water resources and sustain socioeconomic development in arid regions. Understating how vegetation and elevation affect the water yield is crucial for sustainable water management of arid regions. However, the scarce observations, heterogeneous hydroclimatic conditions, and oversimplifications of the energy and biogeophysical processes in traditional hydrological models limit the comprehension of hydrological processes associated with water yield over alpine basins. This study combines the fully distributed WRF-Hydro model with the Budyko framework to characterize the water yield of an alpine basin named Xiying River Basin (XRB) located in Northwest China. Results show that WRF-Hydro driven by the remote-sensing-based products was able to reproduce both observed streamflow and evapotranspiration (ET) in the XRB. The ratio of transpiration to ET was considerably underestimated when only calibrating streamflow. Such underestimation can be solved by calibrating parameters related to soil surface resistance and leaf conductance. Additionally, for the dominant vegetation types (i.e., closed shrublands and grasslands) in the XRB, we found that closed shrublands have a lower water yield capacity than grasslands. Closed shrublands have a stronger ET rate, resulting in stronger soil moisture consumption, lower antecedent soil moisture, and higher soil water deficit, causing higher infiltration loss during rainfall events and lower water yield. Moreover, the water yield capacity increases with the increasing elevation, because the precipitation increases while the ET decreases as the elevation rises, and the topographical slope increases, resulting in lower infiltration, lower baseflow index, and higher water yield capacity. Our results also indicate that afforestation should not be encouraged for grasslands and closed shrublands in areas lower than 2800 m and 3200 m, respectively. Overall, this study provides scientific support for vegetation afforestation planning in the alpine regions.

Spatiotemporal Variation and Factors Influencing Water Yield Services in the Hengduan Mountains, China

Conducting a quantitative assessment of water yield in mountainous areas is crucial for the management, development, and sustainable utilization of water resources. The Hengduan Mountains Region (HDMR) is a significant water-supporting area characterized by complex topography and climate changes. To analyze the spatial and temporal variations of water yield in the HDMR from 2001 to 2020, we employed the InVEST model and examined the influencing factors in conjunction with the elevation gradient. Our results indicate that: (1) The water yield in the Hengduan Mountains decreases from southeast to northwest, with the southwestern and eastern regions having high water yield values, and the high-altitude areas in the northwestern part having low water yield values. (2) The water yield in the Hengduan Mountains exhibits a decreasing trend followed by an increasing trend from 2001 to 2020, with the lowest level in 2011 and higher levels in 2004, 2018, and 2020. (3) Pixel-based trend analysis demonstrates a decreasing trend in water yield in the central and western parts of the study area, while the eastern part shows an increasing trend. (4) The climatic components, particularly precipitation, predominantly influence the spatial and temporal variations of water yield in the Transverse Mountain region. In most areas, evapotranspiration and land surface temperature have a negative impact on water yield. (5) Water yield tends to decrease and then increase on the altitudinal gradient, with precipitation and actual evapotranspiration being the factors directly affecting water yield, and land surface temperature and the proportion of forested areas having a significant indirect effect on water yield. Our study provides a scientific basis for water resources management and sustainable development in the Hengduan Mountains.

Improvement of water yield and net primary productivity ecosystem services in the Loess Plateau of China since the “Grain for Green” project

The Loess Plateau of China is one of the regions with the most serious soil erosion globally. The ambitious “Grain for Green” project was there implemented to restore degraded ecosystems, profoundly changing the water yield and carbon sequestration ecosystem services. To understand the changes of water- and carbon-related ecosystem services (hereafter WCES) in the Loess Plateau, this study combined the CASA (Carnegie-Ames-Stanford Approach) model and InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) model to thoroughly reveal the changes and intrinsic linkages of water yield and net primary productivity since the “Grain for Green” project in the Loess Plateau. The results show that the WCES of the Loess Plateau were increasing since 2001, dominated by both the climate change and human afforestation. The water yield and net primary productivity showed strong synergistic effects in 80% of the Loess Plateau, mainly resulting from the rapid increase of precipitation in recent years. The increasing atmospheric precipitation contributed to more WCES provisions, which may have offset the trade-off between WCES caused by large-scale afforestation. In view of the synergistic effects of WCES, enhancing water input into the ecosystem may be an effective measure to respond with future WCES degradation in dry years, such as artificial basin-cross water transfer project. Despite the low correlation between teleconnection factors and WCES, the low water yield and reduction of net primary productivity may be associated with a strong El Niño event in 2015. This study assists in a wise decision-making on the future “Grain for Green” and ecological management in the Loess Plateau.

Sensitive or resilient catchment?: A Budyko-based modeling approach for climate change and anthropogenic stress under historical to CMIP6 future scenarios

To develop effective adaptation strategies for climate change, particularly in regions where water is scarce, it is crucial to comprehend and quantify how hydrological responses are influenced by anthropogenic activities and climate change. The primary concern nowadays is to identify the hydrologic sensitive and resilient catchment under these diverse conditions. Thus, a framework is developed in this study to analyse the hydrologic sensitivity and resiliency of a catchment incorporating the elasticity-based Budyko approach. The developed framework is applied to three neighbouring catchments (Brahmani, Baitarani, and Subarnarekha) in eastern India that have received less attention in light of resiliency and sensitivity perspectives. The Budyko approach is first applied using hydro-climatic records of historical phase (1979–2018) and then extended for future phase (2025–2064) under four different Shared Socioeconomic Pathways (SSPs) (1-2.6, 2-4.5, 3-7.0 and 5-8.5) of Coupled Model Intercomparison Project Phase 6 (CMIP6) projections which will provide new insights to the hydrological community. The results highlight that streamflow variations of the Subarnarekha is more sensitive to anthropogenic activities in all time phases. In contrast, the Brahmani and Baitarani are more sensitive to climate change in future phases. During historical phase, the Brahmani and Baitarani are identified to be resilient catchments with high water yield and dry climate, whereas the Subarnarekha is found to be sensitive catchment, exhibiting low water yield and dry climate. However, in future phase, all three catchments are predicted to be resilient, characterized by high water yield and wet climate. The major inference from this study is excess anthropogenic activities can disrupt the anticipated hydrological functioning of a catchment, particularly under critical climatic conditions, which can result in decreasing hydrological resiliency. The finding of this study mainly highlights the response of a hydrological system to climate change and anthropogenic activities to explore the approach of sensitivity and resiliency from a socio-hydrological perspective.

Enhanced dew harvest with porous wind covers

Dew harvest with radiative cooling condenser can be a simple and portable solution to extract water from the atmosphere, but its water yield is limited. Implementing wind cover is one of the simplest ways to improve cooling power by reducing convection. However, wind covers usually block water transport and cannot be applied to radiative condensers for dew harvesting. Herein, porous wind covers, including polyethylene (PE) nets and porous PE films, have been adopted, and their effect on radiative condensers has been investigated. These wind covers have good atmospheric window transmittance and convection reduction effect. The two-day radiative cooling experiment has proven that sufficient sub-ambient cooling can be achieved using our radiative cooling film. Afterward, a two-month nocturnal condensation experiment was conducted. Condensers covered with high porosity PE nets on average yield more water than the condenser without cover, with a maximum improvement of 19.5% using a PE net with ∼86% porosity. In particular, at low humidity condition, the average water yield for the condenser without cover is only 1.4 g/m 2 /night. In comparison, the value increases to 23.7 g/m 2 /night and 13.6 g/m 2 /night for condensers covered with a PE net (∼64% porosity) and a porous film (∼4% porosity), respectively. The improvement in water yield indicates that porous wind cover is a simple and essential tool for radiative condensers to provide more water in regions with dry and windy climates. Further analysis has revealed that experimental observations arise from the trade-off between convection suppression and water transportation of the porous wind covers. • Wind cover is a simple tool for radiative condensers to potentially improve water yield. • A maximum water yield increase of 19.5% occurs for condensers in Shanghai with high-porosity cover. • At low water yield, condensers with wind cover can increase the water production by up to 10 times.

Simulating the hydrological impacts of land use conversion from annual crop to perennial forage in the Canadian Prairies using the Cold Regions Hydrological Modelling platform

Abstract. The Red River is one of the largest contributing sources of discharge and nutrients to the world's 10th largest freshwater lake, Lake Winnipeg. Conversion of large areas of annual cropland to perennial forage has been proposed as a strategy to reduce both flooding and nutrient export to Lake Winnipeg. Such reductions could occur either via a reduction in the concentration of nutrients in runoff or through changes in the basin-scale hydrology, resulting in a lower water yield and the concomitant export of nutrients. This study assessed the latter mechanism by using the physically based Cold Regions Hydrological Modelling platform to examine the hydrological impacts of land use conversion from annual crops to perennial forage in a subbasin of the La Salle River basin in Canada. This basin is a typical agricultural subbasin in the Red River Valley, characterised by flat topography, clay soils, and a cold subhumid, continental climate. Long-term simulations (1992–2013) of the major components of water balance were compared between canola and smooth bromegrass, representing a conversion from annual cropping systems to perennial forage. An uncertainty framework was used to represent a range of fall soil saturation status (0 % to 70 %), which governs the infiltration to frozen soil in the subsequent spring. The model simulations indicated that, on average, there was a 36.5 ± 6.6 % (36.5 ± 7.2 mm) reduction in annual cumulative discharge and a 29.9 ± 16.3 % (2.6 ± 1.6 m3 s−1) reduction in annual peak discharge due to forage conversion over the assessed period. These reductions were driven by reduced overland flow 52.9 ± 12.8 % (28.8 ± 10.1 mm), increased peak snowpack (8.1 ± 1.5 %, 7.8 ± 1.6 mm), and enhanced infiltration to frozen soils (66.7 ± 7.7 %, 141.5 ± 15.2 mm). Higher cumulative evapotranspiration (ET) from perennial forage (34.5 ± 0.9 %, 94.1 ± 2.5 mm) was also predicted by the simulations. Overall, daily soil moisture under perennial forage was 18.0 % (57.2 ± 1.2 mm) higher than that of crop simulation, likely due to the higher snow water equivalent (SWE) and enhanced infiltration. However, the impact of forage conversion on daily soil moisture varied interannually. Soil moisture under perennial forage stands could be either higher or lower than that of annual crops, depending on antecedent spring snowmelt infiltration volumes.

High-yielding and stable desalination via photothermal membrane distillation with free-flow evaporation channel

Small-scale desalination devices driven by solar energy is a promising solution for freshwater in remote off-grid islands where centralized energy supplies are hardly accessible. However, the low water yield and unstable operation caused by energy inefficiency and salt precipitation are tricky problems. To provide a reliable freshwater supply, a desalination device with high water yield and no salt precipitation is the main target of this work. A three-stage photothermal membrane distillation module with free-flow evaporation channel was fabricated and a model was developed accordingly. Upon varying flow patterns and flow rates, the effects of different flow configurations on water production and salt concentration were observed and discussed. It is revealed that the feed from the bottom to the top stage in series connection at a flow rate of 28 ml h−1 can achieve a water production rate of 2.23 kg m−2 h−1 and a solar energy utilization efficiency as high as 147.9 % without salt precipitation. This work showed a competitive water production among all the previously reported small-scale solar membrane distillation devices. Besides, the flowing design is effective in preventing salt precipitation. A strong potential in providing qualified household freshwater with salinity rejection over 99 % on remote islands was indicated.

Water yield service influence by climate and land use change based on InVEST model in the monsoon hilly watershed in South China

Based on the data of meteorological, soil, and land use/land cover (LULC), the InVEST model was used to evaluate the water yield service in the middle and upper Ganjiang River region, which is an important ecological function area in the hilly region of South China. This study discusses the value of parameter Z, the impact of climate and LULC change on water yield service, and complements related studies in the monsoon hilly watershed in South China with obvious precipitation change, which is helpful to understand the ecosystem water service functions in this region. The results show that the water yield was closest to the statistical data of total water resources when the parameter Z value of 1.555. The overall distribution of water yield in the MU-GJR was high in the northeast (middle reaches) and low in the southwest (upper reaches), with minimum of 111.8–315.2 mm/a and maximum of 1679.1–2128.4 mm/a from 1980 to 2018. The northeast was a high importance region where high water yield values were clustered, and the southwest was a low importance region where low water yield values were clustered. Water yield was highest in living space and lowest in ecological space. The relationship between land development and water yield service should be coordinated. Climate change had a more significant impact on water yield service than land use change. The results of this study are consistent with the actual situation and help to investigate and identify important areas of water resources in the monsoonal humid zone.

Grassland afforestation

The establishment of tree plantations on native grasslands is expanding in Argentina and Uruguay, prometed by public incentives and, likely, by an emerging market of carbon sequestration. We assessed how this transformation affects the production of ecosystem goods and services, synthesizing preexisting and original information on their influence on biomass production, water dynamics, and nutrient cycling. Field and satellite measurements show that, compared to grasslands, tree plantations in Uruguay, Entre Ríos, and Corrientes had higher primary productivity. This productivity increase was accompanied by higher evapotranspiration rates and a lower water yield, responsible of halving stream flow in afforested watersheds in Córdoba and Uruguay, in agreement with observations on 26 afforested grasslands around the world. In Buenos Aires, where phreatic water is close to the surface, trees used groundwater increasing the salinity of deep soil and the water table. Most of the tree plantations in the region acidified soils and in some cases stream water, mainly as a result of their high calcium consumption. It is urgent to generate information about other impacts of tree plantations such as changes in fire dynamics or invasive species. An integrative understanding of the influence of tree plantations on the production of goods and services will help to development new forestry systems and policies that are more sustainable and useful for society.

Impacts of land use changes on ecosystem services at different elevations in an ecological function area, northern China

Land use changes affect the supply of ecosystem services, which are related to human health and well-being. Demonstration the interaction of land use and ecosystem services play a great role on the social-economic sustainable development. As a typical greatly land use changes and an important ecological function area, Zhangjiakou and Chengde city (Zhangcheng District) exert a profound impact on the sustainable development of the Beijing-Tianjin-Hebei region in northern China. Based on InVEST model, the variations in water yield and soil retention at different elevations in the Zhangcheng District during 2011 and 2015 were illustrated. And the responses of water yield and soil retention to land use changes were revealed as well. The natural and man-made land use have exactly opposite effects on ecosystem services. With the increase of cultivated land, the capacity of water yield increases significantly, while soil retention decreases largely at all elevations (p < 0.05). However, with the increase of arbor land, shrub land, grassland, and water bodies, the capacity of water yield decreases, while soil retention increases at all elevations (p < 0.05). Comparably, the effect of land use changes on water yield depth is greater than that on soil retention; the whole effect of land use changes on ecosystem services is significantly highest at middle elevation. Generally, the lower water yield depth forms, the higher soil retention occurs. This study is helpful for rational regulation of land uses and protection of ecosystem services for both our study area and similar regions.

Analysis of spatio-temporal variation of hydroclimatic variables of the Krishna river basin under future scenarios

Climate change and intensified human activities are expected to alter the natural hydrological cycle would cause changes in distribution of water resources and their availability across space and time. Therefore, the present study focused on understanding the spatiotemporal variations of hydroclimatic variables namely rainfall, surface runoff, water yield, and the Aridity Index (AI) of the Krishna River Basin (KRB) under combined impact of climate and Land Use/Land Cover (LULC) change scenarios. From trend analysis, the best model (CNRM-CM5 driven RCM) projected an increasing trend in rainfall under both RCP 4.5 and 8.5 scenarios for the entire century. Results indicated that, except for the central part, most of KRB experiences high runoff and water yield conditions under both RCP 4.5 and 8.5 scenarios in mid and end centuries, conversely it may face low runoff and water yield conditions in early century. Most of the central part is in arid and semi-arid conditions and, eastern part of the basin is in dry sub-humid conditions, while the Western Ghats, Palleru, and Munneru regions of the basin fall under humid and hyper humid regions under RCP 4.5 scenario. Whereas majority of the basin falls under humid and hyper humid regions under RCP 8.5 scenario except for the central and few other parts of the basin. In light of this, it was essential to review the current water management strategies and plan future projects to provide efficient and effective ways to mitigate the adverse impacts resulting from climate variability.

In situ polymerized Fe2O3@PPy/chitosan hydrogels as a hydratable skeleton for solar‐driven evaporation

AbstractThe world population is severely affected by water scarcity, and it is an alarming issue that needs to be addressed urgently. Seawater desalination by solar‐driven evaporation is a promising technique to produce clean water. However, it is energy intensive and directs to a low water yield under natural sunlight. Therefore, the developments of new photothermal materials can reduce required energy for desired evaporation rates for efficient freshwater yield. Indeed, chitosan and polypyrrole‐based polymers are natural cationic copolymers, and their nanocomposites present well deal of interest for hydrogel structures due to their hydratable skeletons, and solar‐absorbing nature. Here, we report in situ polymerized Fe2O3@PPy/chitosan hydrogels as lightweight evaporation structures for solar‐powered evaporation under brine solutions (3.5 wt%). The polymeric network of Fe2O3@PPy/chitosan hydrogels builds in cross‐linked macroporous water channels, self‐floating, and a wide range of omnidirectional solar absorption (96%). The state‐of‐the‐art evaporation experiments demonstrate an efficient evaporation rate of water (1.80 kg m–2 h–1) and enhanced solar‐to‐vapor conversion efficiency (91%) as compared to other carbon‐based evaporation structures, excluding heat losses under 1 kW m–2 (one sun). Of note, the ultra‐black hydrogel surface stored enough thermal energy (39.6°C) under one sun solar irradiance due to the cationic polymeric network of Fe2O3@PPy/chitosan. A single‐step process for a freshwater supply that has been purified from various contaminants shows the potential of this device for real‐world applications.

Performance assessment of a novel solar distiller with a double slope basin covered by coated wick with lanthanum cobalt oxide nanoparticles

Solar distillers are simple desalination systems used to produce freshwater from saline water by utilizing solar energy. The low water yield is the key drawback of solar distillers. In this work, a novel double slope wick type solar distiller (DSWSD) coated with lanthanum cobalt oxide (LaCoO 3 ) nanoparticles doped in black paint is experimentally investigated. The nano LaCoO 3 /black paint is uniformly speared on the jute wick surface to boost the absorption improvement of solar irradiance for effective desalination. The influence of water flow rate (namely; 0.050, 0.10, and 0.20 kg/min) on the internal mass and heat transfer of the proposed DSWSD is analyzed. The mass and heat transfer coefficients (HTCs) are computed using the experimental results and compared with those computed according to Dunkle’s correlations. Experiments have been conducted on the established DSWSD under climatic conditions of Vijayawada, Andhra Pradesh (16.4419° N, 80.6226° E), India. It is observed that there is an increase in the internal HTCs as well as distilled yield at low flow rates of saline water for the DSWSD. The daily productivity of the proposed DSWSD coated with and without 20 wt % LaCoO 3 /black paint is 5.40 and 3.85 kg/m 2 . day, respectively, at saline water flow rate of 0.05 kg/min. Moreover, the average values of evaporative and convective HTCs as well as energy efficiency are found higher by 11.20%, 17.54%, and 24.86%, respectively, than that of the solar distiller without LaCoO 3 /black paint.

Impacts of Irrigation Time and Well Depths on Farmers’ Costs and Benefits in Maize Production

In the North China Plain, drought usually occurs during the interval between wheat harvest and maize sowing in normal and dry years. The first irrigation for maize plays a critical role in guaranteeing seed germination and grain yields. Using experimental data from Xinxiang in 2019 and survey data of 641 farmers from the North China Plain in 2020, this study adopts a cost-benefit analysis method to investigate the impacts of irrigation time and well depths on farmers’ costs and benefits in maize production. The results showed that farms with well depth &gt; 120 m accounted for 49% of total farms, especially in Hebei Province, and 38% wells had low water yield &lt; 2.7 m3 kW−1 h−1. Delaying the time of the first irrigation made maize yields decline by up to 307 kg ha−1 day−1. Well depths increased irrigation costs and total maize production cost in an exponential manner, causing farmers’ benefits to decrease exponentially with well depths. With well depth &gt; 180 m, the proportion of irrigation cost to total cost rose to 14%, whereas well depth &gt; 230 m directly caused the farmers’ profits negative. A critical well depth of 230 m was put forward as the upper limit for farmers adopting maize planting in the NCP. The concept of ‘rotational irrigation strategy’ and suggestions of adopting drip irrigation, sprinkler irrigation, or hose-reel sprinkler irrigation were recommended to advance 6–8 days for the first irrigation period, compared with traditional flood irrigation.