High Water Stress Research Articles

Multi-criteria decision-making for selecting a solar farm location to supply energy to reverse osmosis devices and produce freshwater using GIS in Iran

Iran has 985,798 square kilometers of desert areas, equivalent to 59.8 percent of the country's total area. This factor causes the creation of salt marshes and, accordingly, the salinization of surface and groundwater. For the first time in this paper, an indirect method is presented to identify areas of Brackish water sources with 3000–10000 mg/L TDS in the entire country of Iran and simultaneously identify the area's potential in terms of the solar energy to provide energy for desalination by reverse osmosis devices. Other types of sources of water, such as seawater, which has more salinity than Brackish water (about 35000 mg/liter) are not investigated in this research, because the primary purpose of this article is to use water that exists in the form of ponds, wells, or surface water that water cannot be used for residential or agricultural purposes, at the same time, this water is not seawater. Simultaneously 16 data layers that include economic, environmental, technical, and geological parameters have been considered.The proposed methodology provides a structured decision aid, which can be used in other countries to identify the mentioned areas and produce fresh water using reverse osmosis devices. Geographic Information Systems (GIS) are used to generate layers of data and to apply the elimination criteria and constraints. Multiple Criteria Decision Analysis (MCDA) is then used to rank and sort the grids via the identified evaluation criteria. This research can also have two other applications. The first is for professionals who want to identify areas with saline water potential, and the second is for organizations that want to launch reverse osmosis desalination plants that work with solar renewable energy. Technically, there are about 160 cities in Iran that have an area of about 144440685120.498077 square meters, have saline water sources, and simultaneously have the potential to use solar energy as one of the renewable energy sources to power reverse osmosis desalination devices. Most of these areas are located in the east of Iran and these areas have high water stress. In this research, the city of Khansar with an area of 95917147.16 square meters, which is located in the province of Isfahan and in the central part of Iran, has surface and underground saline water resources that both technically and operationally, has the highest potential.

Untargeted metabolomics revealed essential biochemical rearrangements towards combined heat and drought stress acclimatization in Pinus pinaster

Trees usually face simultaneous stresses and have evolved to deal with them naturally. However, as a consequence of climate change, heat waves and drought stress have become more intense, frequent, and long-lasting than the adaptative capacity of trees. How trees can cope with stress and acclimate will benefit our forest management and genetic improvement programs aimed to maintain forest sustainability. Maritime pine has a remarkable adaptive capacity, based on its metabolic plasticity, which allows this specie to grow in a wide range of climatic conditions. Consequently, this work aims to investigate P. pinaster metabolome in response to different intensities of combined stresses. To assess the acclimation gradual changes to heat and drought stress, we established a five-time-point experiment simulating a seven-day heat wave (temperature reaches 30 ºC and 40 ºC) accompanied by different water availability. Low-intensity stresses (30 ºC and low water stress) provoked metabolic acclimation accumulating those compounds necessary if the environmental conditions worsen and stress intensity increases. The main pathways involved were amino acid and carbohydrate metabolism leading to an enhanced accumulation of phenolics, flavonoids, and terpenoids. When plantlets were exposed to high-intensity stress (40 ºC and high water stress), secondary metabolism took a prominent role, through alkaloids, lignans, and glycosyloxyflavones. Overall, this work provides new insights into the metabolic mechanisms under both stresses and pointed out the need to combine stresses and intensities, as plant responses are not predictable from the study of isolated stresses.

Analysis of soil water potential characteristics of wheat croplands and apple orchards in an agroforestry ecosystem based on the van Genuchten model

Due to intense droughts and water shortages, soil water deficit limits agricultural production in arid and semiarid areas, such as China’s Loess Plateau region. Yet the effects of different cover crops on soil water in these areas have received insufficient attention. This study was conducted in the Weibei rainfed highland to investigate soil water potential dynamics in an agroforestry ecosystem comprising winter wheat (<i>Triticum aestivum</i> L.) and apple (<i>Malus domestica</i>) trees over the apple growth period (March to September of 2020). Soil water characteristic curves (SWCCs) of cropland topsoil (0 to 40 cm), orchard topsoil (0 to 40 cm), dark loessial subsoil (40 to 80 cm), and loess parent material (80 to 150 cm) were determined using the centrifuge method and water vapor equilibrium method. The van Genuchten model was used to fit SWCCs and then convert volumetric soil water content monitored in field plots to soil water potential. A quantitative analysis was conducted to evaluate soil water stress in wheat croplands and apple orchards. The model performed well in fitting SWCCs for all tested soils, yielding a robust accuracy (<i>R</i>² &gt; 0.96). Compared to apple trees, wheat was more threatened by drought. From mid-March to early July, the 0 to 100 cm soil layers of croplands all exhibited high water stress with matric suction pF &gt; 3.98, and unavailable water occurred in the 0 to 20 cm and 0 to 80 cm soil layers in late March to late April and mid-May to mid-July, respectively. Drought threat in apple orchards increased with an increase in tree age. In young orchards (&lt;10 y), high water stress was found only in surface soil layers (0 to 20 cm) in mid-March to late April and late May to early July, which spread to a depth of 70 cm in early June to early July. In mature orchards (10 to 20 y), high water stress was similarly observed in the surface soil layers in mid-March to early May and late May to early July, which extended to the 80 cm depth in late May to early July. In old orchards (&gt;20 y), high water stress initially emerged in the surface soil layers in early April to mid-April and then reached the 70 cm depth in late May to mid-July, whereas unavailable water occurred in the 0 to 60 cm soil layers in mid-June to mid-July. The results indicated that soil water stress zones with low water potential were formed intermittently at different soil depths of apple orchards depending on tree age and growth stage. However, compared to wheat croplands, apple orchards were less influenced by drought stress, so that converting croplands to orchards could alleviate drought threats in the Weibei area.

Positive effects of warming do not compensate growth reduction due to increased aridity in Mediterranean mixed forests

AbstractIncreased winter and early spring temperatures due to climate change can enhance forest productivity due to earlier growth onset in temperate regions. However, drought‐prone forests can be highly vulnerable to the combined effect of high summer temperatures and water stress. Understanding how water stress and rising temperatures along the growing season control tree growth in co‐occurring species with contrasting drought tolerances is key to project climate change effects on forest dynamics. Here, we evaluated the interactive effect of seasonal temperature and water availability on annual radial growth and climate–growth instability over six decades (1951–2015) in three pine species with contrasting drought tolerances (Pinus pinaster, Pinus nigra, and Pinus sylvestris). For this, we retrospectively observed radial tree growth using dendroecological methods and evaluated seasonal temperature and water availability effects by using linear mixed models. Early growing season temperature and water availability had a positive effect on tree growth, but the positive effect of late season temperature was modulated by water availability. Moving time‐window analyses revealed temporal instability in climate–growth relationships. Since the 1980s, pine species showed a higher growth sensitivity to both seasonal temperatures and annual water availability. Furthermore, growth reductions were more pronounced due to increased summer temperatures and reduced precipitation. Our results were similar for the three studied pine species despite their contrasting tolerance to drought. Overall, climate warming effects on pine growth are contingent upon water availability in Mediterranean continental forests. Synchronization among species, climate–growth instability, and negative growth trends suggests an increased vulnerability to drought of Mediterranean pine species in response to ongoing climate change.

Evaluating four remote sensing based models to estimate latent heat flux in semi-arid climate for heterogeneous surface coverage of western Algeria

Optimal estimation of water balance components at the local and regional scales is essential for many applications such as integrated water resources management, hydrogeological modelling and irrigation scheduling. Evapotranspiration is a very important component of the hydrological cycle at the soil surface, particularly in arid and semi-arid lands. Mapping evapotranspiration at high resolution with internalised calibration (METRIC), trapezoid interpolation model (TIM), two-source energy balance (TSEB), and soil-plant-atmosphere and remote sensing evapotranspiration (SPARSE) models were applied using Landsat 8 images for four dates during 2014–2015 and meteorological data. Surface energy maps were then generated. Latent heat flux estimated by four models was then compared and evaluated with those measured by applying the method of Bowen ratio for the various days. In warm periods with high water stress differences and with important surface temperature differences, METRIC proves to be the most robust with the root-mean-square error ( RMSE) less than 40 W∙m –2. However, during the periods with no significant surface temperature and soil humidity differences, SPARSE model is superior with the RMSE of 35 W∙m –2. The results of TIM are close to METRIC, since both models are sensitive to the difference in surface temperature. However, SPARSE remains reliable with the RMSE of 55 W∙m –2 unlike TSEB, which has a large deviation from the other models. On the other hand, during the days when the temperature difference is small, SPARSE and TSEB are superior, with a clear advantage of SPARSE serial version, where temperature differences are less important.

Analyzing the impact of extreme heat events and drought on wheat yield and protein concentration, and adaptation strategies using long-term cultivar trials under semi-arid conditions

Extreme weather events, lower precipitation and higher temperatures play a relevant role in the assessment of wheat yield and protein concentration under future weather conditions in Mediterranean environments. To explore this topic, a dataset of long-term wheat cultivar trials carried out in 17 locations in Andalusia, southern Spain, between 1990 and 2017, and covering a wide range of weather conditions, has been analyzed.The occurrence of maximum temperatures surpassing 32.5°C during heading showed significant correlations with yield, and generated reductions of up to 30% of the maximum observed yield. Similarly, water stress up to 20 days after heading or numerous days with both high temperatures and water stress up to 45 days after heading, also showed significant correlations with yield, and generated reductions of up to 23% and 41%, respectively. Moreover, irrigation showed a very relevant role, with the minimum relative yield increasing from 9% under rainfed conditions to 56% with irrigation supply higher than 150mm. For protein concentration, frequent joint events combining mild temperatures and severe water stresses around heading showed increases of 3 %-units. The future weather conditions projected for southern Spain will enhance risk of yield reduction and protein concentration increases, with a high spatial variability.Earlier sowing dates reduce the coincidence of extreme weather events with critical crop development stages, and thus the effects on yield and protein concentration, even identifying conditions that the impact was fully reversed. Similarly, irrigation during heading mitigated the negative effects of water stress on yield and the positive effects on protein concentration.The combination of long-term cultivar trials under semi-arid weather conditions, modeling and future climate projections constitutes an excellent tool for the assessment of vulnerable/suitable areas, and for the identification of site-specific adaptation measures to ensure the sustainability of wheat-growing areas in southern Europe.

Comparison of water stress regarding potential shale energy development in China and the US

Unconventional shale resources are important options in mitigating intensified energy challenges. Little is known regarding the national-scale water stress induced by the demand-and-supply contradiction during shale development. We here propose a new life-cycle-based model for estimating water intensities of single shale wells and use them as proxies to calculate the water stress facing China and the US. In China, most shale provinces have low water stress (< 1); Xinjiang has the highest one (∼10) so that either long-distance water diversion or groundwater extraction from deep aquifers would be required. The water stress facing the US is not as optimistic as China due to generally lower water availability; Louisiana, Texas, Arkansas, Colorado, and Pennsylvania have the highest water stress (between 10 and 25 under high intensity). We also find that policy combinations can effectively mitigate the water stress and suggest that deep cooperation be desired among those shale -rich countries.

Small‐bodied fish species from the western United States will be under severe water stress by 2040

AbstractHuman need to appropriate freshwater in combination with climate change has intensified the rapid decline in freshwater biodiversity. Based on 216 currently imperiled freshwater species in the United States, the Southwest, and the Rocky Mountains, were predicted to experience the highest increase in future water stress for 2040 in 41 minor watersheds. Resident‐small species in the Southwest, found in single locations (21.6%) or on local level (62.2%), were listed as endangered (n = 37) and are predicted to experience severe water stress increases by 2040. Endangered species in the Rocky Mountains (n = 9), were found on a basin or local level (33.3%), exhibiting predominantly potamodromous behavior (66.7%). Furthermore, many endangered species in key regions lack life‐history data (41%). Our results highlight that determining priority of species for conservation using biodiversity as an indicator may not be useful for identifying future impacts to imperiled species, since many regions undergoing high water stress did not coincide with biodiversity hotspots.

Multi-criteria decision for selecting a wind farm location to supply energy to reverse osmosis devices and produce freshwater using GIS in Iran

Due to its location in arid and semi-arid climates, Iran is one of the countries with the highest water stress, and the need for a study that states a solution for using salt water is felt more than ever. For the first time in this paper, an indirect method is presented to identify areas prone to salty water in the entire country of Iran, which simultaneously have the potential of wind energy to supply electricity for reverse osmosis desalination devices. Simultaneously economic, environmental, technical, and geological parameters have been considered. The proposed methodology provides a structured decision aid, which can be used in other countries to identify the mentioned areas and produce fresh water using reverse osmosis devices. Geographic Information Systems (GIS) are used to generate layers of data and to apply the elimination criteria and constraints. Multiple Criteria Decision Analysis (MCDA) is then used to rank and sort the grids via the identified evaluation criteria. Seventy-eight cities in Iran, mainly located in the east of the country, were identified as potential areas, and 16 cities with the best conditions for using wind energy in the supply of reverse osmosis energy were identified, which are areas with operational potential. For each cubic meter of saltwater desalination at 25 °C, about 0.38 kWh of electricity is consumed, the amount of water that can be desalinated depends on the amount of electricity produced by wind turbines. If the total amount of water that can be operationally extracted through 550 kW turbines can be exploited, it can supply 63.8475% of the country's water needs . About 11658552.6321 cubic meters of water can be desalinated and used. Torbat-e-Jam, located in Khorasan Razavi province, can produce 2244868.421 cubic meters of fresh water, the most prone among other areas.

Assessment of water stress effects on red beet under the Mediterranean conditions

Although there are numerous scientific data on the response of various plants to water stress, there are few studies on red beet in the literature, and non-specifically under the Mediterranean conditions. This study aimed to investigate the effects of water stress (WS) levels (control-WS0, low-WS20, medium-WS40, high-WS60, and extreme-WS80) on water use, growth, yield parameters, and yield response factor of red beet (Beta vulgaris) in Mediterranean conditions. During the growing season, the highest daily evapotranspiration values were 3.7, 2.8, 2.1, 1.4, and 0.7 mm for the control treatment, low, medium, high, and extreme water stresses, respectively. Soil salinity, plant height, fresh leaf yield, and storage-root yield values were decreased as water stress increased. However, there were no significant differences in soil pH, taproot length, and plant water use efficiency between treatments. Significantly important strong- or moderate-positive linear correlations were observed between soil salinity, evapotranspiration, plant height, fresh leaf yield, and storage-root yield values. The yield response factors for red beet storage-root and fresh leaf yields were found to be 0.88 and 0.98, respectively. The results revealed that red beet is slightly tolerant to water stress, with comparatively lower storage-root and fresh leaf yield reductions under the reduced evapotranspiration caused by water stress.

Global and regional models for identification of cooling technology in thermal power generation for water demand estimations in water-energy nexus studies

Water-energy nexus studies aim to connect the process of power generation with the corresponding water demand. The lack of information on the currently installed cooling systems at individual power plants is a challenge for the assessment of the water use on the power plant-level, which complicates decision-making in water management, especially in water-stressed regions. In this study, we investigate the spatial and temporal trends in cooling technology installations globally. Based on that, we propose a machine learning model for cooling technology identification on a regional and global level, which uses a combination of feature selection and classification algorithms. The global model demonstrates an average test set accuracy of 85.42%, which corresponds to only a minor underestimation of the actual global water footprint of 1.78% when the cooling technology and water footprint of individual power plant units is unknown. Apart from that, a special emphasis was placed on regions characterized by high and extremely high water stress, where mistakes in water policy planning and water management may lead to an unsustainable water use or even to an overexploitation of water resources. In these regions, the calculated test set accuracy was 80.83%, which is significantly larger than the average accuracy of a majority class model. The results and the method proposed in this study enable cooling system identification in individual power units using information available from other sources, such as the water stress score or seasonal freshwater availability in the region.

Analyses of the Impact of Soil Conditions and Soil Degradation on Vegetation Vitality and Crop Productivity Based on Airborne Hyperspectral VNIR–SWIR–TIR Data in a Semi-Arid Rainfed Agricultural Area (Camarena, Central Spain)

Soils are an essential factor contributing to the agricultural production of rainfed crops such as barley and triticale cereals. Changing environmental conditions and inadequate land management are endangering soil quality and productivity and, in turn, crop quality and productivity are affected. Advances in hyperspectral remote sensing are of great use for the spatial characterization and monitoring of the soil degradation status, as well as its impact on crop growth and agricultural productivity. In this study, hyperspectral airborne data covering the visible, near-infrared, short-wave infrared, and thermal infrared (VNIR–SWIR–TIR, 0.4–12 µm) were acquired in a Mediterranean agricultural area of central Spain and used to analyze the spatial differences in vegetation vitality and grain yield in relation to the soil degradation status. Specifically, leaf area index (LAI), crop water stress index (CWSI), and the biomass of the crop yield are derived from the remote sensing data and discussed regarding their spatial differences and relationship to a classification of erosion and accumulation stages (SEAS) based on previous remote sensing analyses during bare soil conditions. LAI and harvested crop biomass yield could be well estimated by PLS regression based on the hyperspectral and in situ reference data (R2 of 0.83, r of 0.91, and an RMSE of 0.2 m2 m−2 for LAI and an R2 of 0.85, r of 0.92, and an RMSE of 0.48 t ha−1 for grain yield). In addition, the soil erosion and accumulation stages (SEAS) were successfully predicted based on the canopy spectral signal of vegetated crop fields using a random forest machine learning approach. Overall accuracy was achieved above 71% by combining the VNIR–SWIR–TIR canopy reflectance and emissivity of the growing season with topographic information after reducing the redundancy in the spectral dataset. The results show that the estimated crop traits are spatially related to the soil’s degradation status, with shallow and highly eroded soils, as well as sandy accumulation zones being associated with areas of low LAI, crop yield, and high crop water stress. Overall, the results of this study illustrate the enormous potential of imaging spectroscopy for a combined analysis of the plant-soil system in the frame of land and soil degradation monitoring.

The growing water crisis in Central Asia and the driving forces behind it

Central Asia (CA) is one of the most severe water crisis areas on earth, which has seriously limited the achievement of sustainable development goals (SDGs) in the region. However, a multi-perspective analysis on the process and driving factors of the water crisis in CA has not been conducted. Therefore, we assess the water crisis from multiple perspectives using the water stress index (WSI), safe drinking water and water pollution indicators, and quantitatively analyze the impact of climate change, population growth, poverty, urbanization and transboundary river management on the water crisis. Results show that the water crisis in CA is intensifying. Uzbekistan and Turkmenistan belong to the “severe water stress” category, and the WSIs are increasing in both countries. Tajikistan is classified as “high water stress”. Kyrgyzstan and Kazakhstan both exhibit “moderate water stress”. Moreover, the proportion of the rural population with access to safe drinking water is significantly lower than that of the urban population in all the CA countries. The impact of human activities on water crisis in CA is more significant than that of climatic factors. Both cultivated land area and population are significant factors affecting the water crisis in CA (p < 0.05), with the regression coefficients of 0.62 and 1.62, respectively. Our research provides an essential reference for the sustainable management of water resources and warns that the water security situation in CA will worsen if no effective action is taken.

Glacier Contributions to River Discharge During the Current Chilean Megadrought

AbstractThe current Chilean megadrought has led to acute water shortages in central Chile since 2010. Glaciers have provided vital fresh water to the region's rivers, but the quantity, timing and sustainability of that provision remain unclear. Here we combine in‐situ, remote sensing and climate reanalysis data to show that from 2010 to 2018 during the megadrought, unsustainable imbalance ablation of glaciers (ablation not balanced by new snowfall) strongly buffered the late‐summer discharge of the Maipo River, a primary source of water to Santiago. If there had been no glaciers, water availability would have been reduced from December through May, with a 31 ± 19% decrease during March. Our results indicate that while the annual contributions of imbalance ablation to river discharge during the megadrought have been small compared to those from precipitation and sustainable balance ablation, they have nevertheless been a substantial input to a hydrological system that was already experiencing high water stress. The water‐equivalent volume of imbalance ablation generated in the Maipo Basin between 2010 and 2018 was 740 × 106 m3 (19 ± 12 mm yr−1), approximately 3.4 times the capacity of the basin's El Yeso Reservoir. This is equivalent to 14% of Santiago's potable water use in that time, while total glacier ablation was equivalent to 59%. We show that glacier retreat will exacerbate river discharge deficits and further jeopardize water availability in central Chile if precipitation deficits endure, and conjecture that these effects will be amplified by climatic warming.

How guest profile and tourist segment explain acceptance of economic-based water-saving measures. A mediterranean destination case study

Saving water in tourist destinations is most effective when guests staying in rental accommodation actively participate and collaborate in it, especially in regions where water is scarce, such as the Mediterranean. There are several guest-centred water-saving measures that may be significant and therefore play an important role in saving water, including economic ones. Measures such as taxes and/or economic incentives may be worth considering as a complement to existing water-saving actions. However, little is known about how acceptable they are to guests. To research the acceptance of these measures to guests with different profiles, 493 guests from five hotels, selected by a convenience sampling approach, were surveyed. These hotels - in the Ter River basin, a region with high water stress - stand out for their good water-saving practices. A two-step cluster analysis has been applied to analyse how acceptance of a water tax and a water incentive can be explained by the three resulting clusters. The results demonstrate the water incentive-based measure to be clearly cluster-dependant, a fact that allows to state that the design and application of an economic-based environmental measure need to consider the specific territorial characteristics of the tourist destination. This study explores potential strategies for saving water in a tourist destination facing important challenges regarding climate change and water availability since it allows for the formulation of multiple solutions to reduce water consumption dealing with water scarcity, and sheds new and important light on water resource management in tourist areas. It also highlights the essential role that visitors should adopt in relation to sustainable water consumption during their holiday, making them, together with Destination Management Organizations and the business sector, fundamental stakeholders in the sustainable use of natural resources.

Influence of water stress on engineering characteristics and oil content of sunflower seeds

Knowing some physical and mechanical characteristics and oil percentage of sunflower seeds could be useful for harvesting and processing equipment and activities such as transportation, storage, food production processes and establishing database of this seed. The main aim of this research was to study the effect of water stress during irrigation on seed’s properties and quality. For this purpose, a field experiment was done under four deficit irrigation treatments [80%, 60%, 100–80 (100% irrigation requirement ETc to seed formation, and then reduced to 80% until harvesting) and 100–60% (100% ETc to seed formation, and then reduced to 60% until harvesting)] in comparable with full irrigation (100%). Geometrical, gravimetrical and mechanical characteristics as well as oil seed content and yield of sunflower seed were estimated. Result showed that there was no significant effect of low (100–80%) and medium (80%) irrigation deficit treatments on geometrical, gravimetrical and mechanical characteristics, while applying 60% of irrigation requirement (ETc) showed a significant effect on them. On the other hand, low and medium irrigation stress treatments improved the oil yield and seed oil content. The highest increase was 8.54% and 5.6% for oil yield and oil content respectively, considering T100–80 followed by applying 80% ETc, but with high water stress (60% ETc) oil yield and seed oil content significantly decreased.

Material extraction potential of desalination brines: A technical and economic evaluation of brines as a possible new material source

The environmental threat of discharging highly saline desalination brine into the sea and an expected growth in global demand for raw materials have increased interest in the idea of integrating desalination and material extraction. This paper examines the material extraction potential of desalination brines corresponding to the seawater desalination volume required to meet the projected global demand for freshwater. The results show that a growing use of seawater desalination techniques to solve the upcoming high water stress provides an increased material extraction potential by 2050, particularly for highly concentrated materials. For example, in the studied scenario, the extraction potential for magnesium and lithium in 2050 is approximately 2243 and 3.1 times the corresponding 2018 production, respectively. The analysis shows that the estimated lithium potential may be sufficient to ameliorate the expected shortage over this century, while the magnesium potential can significantly exceed the future demand. Several seawater materials with low concentrations do not have adequate 2050 extraction potential to be considered a viable resource even compared to present production. This study shows that the promising resource potential of desalination brines for elements such as lithium requires development of suitable extraction techniques that overcome the identified techno-economic challenges.

High suspended solids removal of Indian drain water with a down-scaled Dissolved Air Flotation (DAF) for water recovery. Assessing water-type dependence on process control variables

The Barapullah drain crosses through New Delhi, India, and transports millions of cubic meters of stormwater, municipal sewage and industrial sewage to the Yamuna River. Seasonal variations and ambiguous annual discharges cause 20-fold fluctuations in hydraulic flows, pollutants type and concentration. Furthermore, New Delhi is among the most densely populated areas on the planet, with limited surface area and high water stress. Dissolved Air Flotation (DAF) units are known to be highly compact, robust, and an efficient suspended solids separation technology that enables further water recovery in a treatment train. Thus, a down-scaled column DAF was designed and used to determine the total suspended solids removal efficiencies, under different influent conditions. Three influents that resemble the Barapullah drain seasonal variations in composition, and a fourth that imitates the feed of DAF when located after an anaerobic bioreactor were tested. A total of 60 batch DAF experiments were completed and used to assess seven independent control variables for DAF operation, which are influent Total Suspended Solids (TSS), pH, temperature, DAF particles residence time, white water pressure, coagulants and flocculants concentration, and coagulation and flocculation time. Results showed that the down-scaled DAF could be steered from low to high removal efficiencies, comparable to full-scale systems. Maximum TSS removal varied between 92 and 96%. The effect and statistical relevance of the different performance variables on the measured separation efficiencies depended on the influent type. All variables, except temperature and pH, had a significant performance effect with a p-value below 0.1, for at least one influent. Pressure had a positive effect on separation efficiency, due to its importance in bubble formation. Moreover, the down-scaled DAF system had low removal efficiency for particles with spherical shapes, and diameters below 10 µm. Based on the high TSS removal for all tested influents, and the effect of the studied control variables, a full-scale DAF could efficiently remove the suspended solids of the Barapullah drain. The unit robustness for different flows and pollutant concentrations, and small footprint, show DAF suitability as part of a treatment train for water recovery, in densely populated areas.

Sustainability of Costa Rica’s water supply under climate change scenarios

Water scarcity and the difference between water supply and consumption is an increasing concern particularly under climatic uncertainty. Costa Rica has historically been at the forefront of environmental legislation; however, the water use framework in Costa Rica, still utilizes a quota style water allocation, which is problematic in extreme drought conditions. This allocation system paired with climate volatility makes it essential to quantify the future water demands compared to the water supply in Costa Rica. We use the Integrated Valuation of Ecosystem Services and Tradeoffs modeling system to quantify the water availability and usage in watersheds in Costa Rica under different climate and land cover change scenarios. We subsequently assess the spatial variability of water shortage and stress across Costa Rica. We find that there is a high spatial difference in water availability which do not match high use basins. In the highest demand areas, over 70 % of the water supply is projected to be consumed under a business-as-usual land cover change and high emission climate scenario. Low emission climate scenarios result in higher water availability, and increased forest regrowth increases water availability. Overall, the Guanacaste Province and the central valley which includes the capital city of San Jose are most at risk for experiencing high or moderate water shortage and stress in the future. Given the risks associated with water shortage and scarcity, it is important to address governance and stakeholder concerns as we move into the future.

Comparison of Heat and Drought Stress Responses among Twelve Tartary Buckwheat (Fagopyrum tataricum) Varieties.

The use of orphan crops could mitigate the effects of climate change and improve the quality of food security. We compared the effects of drought, high temperature, and their combination in 12 varieties of Tartary buckwheat (Fagopyrum tataricum). Plants were grown at 21/19 °C or 28/26 °C under well-watered and water-stressed conditions. Plants were more discriminated according to environmental conditions than variety, with the exception of Islek that was smaller and produced fewer leaves, inflorescences, and seeds than the other varieties. The combination of high temperature and water stress had a stronger negative impact than each stress applied separately. The temperature increase stimulated leaf and flower production while water stress decreased plant height. Leaf area decreased with both temperature and water stress. High temperature hastened the seed initiation but negatively affected seed development such that almost all seeds aborted at 28 °C. At 21 °C, water stress significantly decreased the seed production per plant. At the physiological level, water stress increased the chlorophyll content and temperature increased the transpiration rate under well-watered conditions. High temperature also increased the polyphenol and flavonoid concentrations, mainly in the inflorescences. Altogether, our results showed that water stress and temperature increase in particular negatively affected seed production in F. tataricum.