Higher Water Use Research Articles

Plant water use related to leaf traits and CSR strategies of 10 common European green roof species

The vegetation layer contributes to multiple functions of green roofs including their hydrological function as plants remove water from substrates between rainfall events through evapotranspiration, restoring the green roofs storage capacity for rainfall retention. While individual traits have been related to water use strategies of green roof plants, these traits are inconsistent, suggesting the importance of trait combinations which may be reflected in CSR (competitor, stress tolerator, ruderal) strategies. Therefore, relating plant water use to leaf traits and CSR strategies could help facilitate green roof plant selection into new geographical regions where green roof technology is developing. For example, in high latitude northern European regions with long daylight during the growing season. Growth (shoot biomass, relative growth rate and leaf area), leaf traits (leaf dry matter content, specific leaf area and succulence) and CSR strategies were determined of 10 common European green roof plants and related to their water use under well-watered (WW) and water-deficit (WD) conditions. All three succulent species included in the experiment showed mostly stress tolerant traits and their water loss was less than the bare unplanted substrate, likely due to mulching of the substrate surface. Plants with greater water use under WW conditions had more ruderal and competitive strategies, and greater leaf area and shoot biomass, than species with lower WW water use. However, the four species with the highest water use under WW conditions were able to downregulate their water use under WD, indicating that they could both retain rainfall and survive periods of water limitations. This study indicates that, for optimal stormwater retention, green roof plant selection in high latitude regions like northern Europe, should focus on selecting non-succulent plants with predominantly competitive or ruderal strategies to make the most of the long daylight during the short growing season.

Model-based climate change adaptational potential and productivity of some cowpea genotypes and its sensitivity to bias adjustment

Grain legumes are essential for the protein supply to an ever-growing population in Africa. However, little is known about the adaptational potential and thus resilience to abiotic stress of major grain legumes under future climatic change for the evaluation of climate change impact and adaptation. This study assessed the adaptation potential of some cowpea genotypes to future climate change in the moist (Kumasi—Ghana) and dry savanna (Ouagadougou—Burkina Faso) biomes of West Africa based on a validated process-based SIMPLACE model using the output of four global circulation models (GCMs) for two shared socioeconomic pathways (SSPs, i.e., ssp126 and 585). In addition, it assesses the sensitivity of the cowpea model to bias corrections of the GCM outputs. In comparison of future socioeconomic pathways with historic time series, the use of bias-corrected climate model output slightly increased the rate of the phenological development of the genotypes in the future period except in Ouagadougou, in the ssp585 scenario. Without bias correction, this increase of the rate of phenological development in the future scenarios was less pronounced. With bias correction, the total aboveground biomass and yield of all genotypes were reduced in both SSPs. The change in the average water stress and phosphorous stress were genotype specific. Despite a general yield decline in both SSPs, the genotypes Asontem and GH6060 exhibited the adaptational potential to future climate change in the moist and dry savanna biomes. This is by a higher accumulation of total aboveground biomass, higher yield, and tolerance to high temperature as well as high water use and photosynthetic efficiency due to higher atmospheric carbon dioxide concentrations, despite faster phenological development.

Exploring tomato phenotypic variability under combined nitrogen and water deficit

BackgroundDespite drought and nitrogen (N) deficit being two of the most important crops’ growth limiting factors, only few studies have explored tomato phenotypic variability in response to both abiotic stresses.AimsIn this study, we aimed to perform a phenotypic evaluation and an analysis of the growth traits of 40 tomato genotypes (mostly focusing on old cultivars, but also including modern hybrids and wild tomato relatives’ accessions as anchors) grown in pots that were subjected to combined N and water deficit.MethodsEach genotype was divided into two groups: control (100% N, 100% field capacity) and combined deficit (20% N, 50% field capacity). A total of 14 morpho-physiological traits were evaluated and further analyzed using multivariate statistical methods.ResultsThe Principal Component Analyses revealed considerable phenotypical diversity among tomato genotypes, with four principal components explaining 82% of the variability. Data integration on a cluster analysis separated the studied genotypes into three distinct clusters based on their ability to handle the combined deficit. Tolerance was associated with traits such as lower specific leaf area, lower leaf area ratio and higher water use efficiency, comparing to the sensitive genotypes.ConclusionsThis study shows that tomato tolerance to combined N and water deficit largely varies between genotypes and that old cultivars represent a valuable gene pool towards more sustainable food production systems.

COMPARATIVE BETWEEN WATER LEVEL AND SOIL COVER MATERIAL ON GROWTH, PRODUCTIVITY AND WATER USE EFFICIENCY OF HOT PEPPER PLANT

Two field experiments were conducted during the two successive winter seasons of 2020-2021 and 2021-2022 on the experimental farm belonging to the Central Laboratory for Agricultural Climate, Agricultural Research Center, Giza Governorate, and Egypt. The study comprised three irrigation levels (50, 75, and 100% of estimated water requirement based on climatic data) and four soil cover treatments namely transparent polyethylene mulch (PE), rice straw (RS), date palm fiber wastes (DPf) and control (bare soil). Hot pepper seeds (Capsicum annuum L.), Super Noura F1 hybrid. Hot pepper transplants were cultivated in the field in the first week of September for both seasons. The main results show that using 100% water level led to increased vegetative and yield of hot pepper during both seasons followed by using 75% while deficit irrigation gave the lowest hot pepper growth and yield. Using 75% water level gave the highest water use efficiency. Using PE mulch led to increasing the soil temperature during the growth season followed by rice straw mulch whereas the date palm fiber wastes mulch decrease soil temperature during both seasons. Moreover, PE treatment led to an increase in the growth and yield of hot pepper during both seasons. Control treatment combined with a 50% water level decreased the growth and productivity of hot pepper during the two seasons.

Seasonal variations of plant water use in the karst desertification control

Understanding the water use characteristics of plants is crucial for the sustainability of forest water management and vegetation restoration. The vegetation restoration program in the karst desertification areas of southwest China has been implemented for more than two decades, and remarkable achievements have been made in ecological restoration. However, the water use characteristics of revegetation are still poorly understood. We investigated the water uptake patterns and water use efficiency of four woody plants (Juglans regia, Zanthoxylum bungeanum, Eriobotrya japonica, and Lonicera japonica) using stable isotopes (δ2H, δ18O, and δ13C) in combination with the MixSIAR model. The results showed that plants responded to seasonal changes in soil moisture with flexible water uptake patterns. Differences in water use sources among the four plant species during the growing season indicated the occurrence of hydrological niche separation, which is the key to vegetation symbiosis. Throughout the study period, groundwater made the lowest contribution to plants (9.39 %~16.25 %), and fissure soil water made the highest contribution (39.74 %~64.71 %). Among them, shrubs and vines were more dependent on fissure soil water compared to trees (50.52 %~64.71 %). Furthermore, plant foliar δ13C was higher in the dry season than in the rainy season. Evergreen shrubs (−27.94 ‰) exhibited higher water use efficiency compared to other tree species (−30.48 ‰~−29.04 ‰). The water use efficiency of four plants showed seasonal variation and was influenced by the water availability caused by soil moisture. Our study demonstrates that fissure soil water is an important water source for karst desertification revegetation and that seasonal changes in water use characteristics are influenced by species-level water uptake patterns and water use strategies. This study provides a reference for vegetation restoration and water resource management in karst areas.

Enhancing growth, yield and water use efficiency of rice (Oryza sativa) through drip irrigation

A field experiment was conducted during rainy (kharif) season of 2018 and 2019 at the research farm of Tamil Nadu Rice Research Institute, Aduthurai, Tamil Nadu to evaluate the impact of drip irrigation on rice (Oryza sativa L.) growth, productivity and water use efficiency. The experiments were laid out in a strip plot design with 4 varieties/hybrids in the horizontal strip and 6 irrigation regimes in the vertical strip with 3 replications. The findings reveal that drip irrigation at 125% Pan Evaporation (PE) resulted in superior growth, yield parameters and grain yield. KRH 2 with 125% PE recorded the maximum grain yield (4200 kg/ha), followed by ADT 45 (4140 kg/ha) with 125% PE. All yield attributes, except ill-filled grains/panicle, increased with increasing irrigation level from 50 to 125% PE. Rice yield attributes, viz. tillers/m2 (r=0.86), panicles/m2 (r=0.90) and grains/panicle (r=0.84) showed positive correlation with grain yield. Irrespective of the variety and irrigation levels the row closer to the drip line recorded higher grain yield at all the irrigation levels compared to rows farthest. Among the irrigation regime the highest total water use (671 mm) was recorded in 125% PE while the highest water use efficiency (6.5 kg/ha-mm) was recorded in 75% PE up to tillering stage, 100% PE during flowering phase and 75% PEduring maturity phase. Among the variety, ADT 45 recorded the highest water use efficiency (7.15 kg/ha mm). The study recommends KRH 2 hybrid and ADT 45 variety for drip irrigation with 125% PE in areas with limited water availability, especially in well-irrigated areas.

Ameliorating the drought stress tolerance of a susceptible soybean cultivar, MAUS 2 through dual inoculation with selected rhizobia and AM fungus

BackgroundDrought stress is currently the primary abiotic stress factor for crop loss worldwide. Although drought stress reduces the crop yield significantly, species and genotypes differ in their stress response; some tolerate the stress effect while others not. In several systems, it has been shown that, some of the beneficial soil microbes ameliorate the stress effect and thereby, minimizing yield losses under stress conditions. Realizing the importance of beneficial soil microbes, a field experiment was conducted to study the effect of selected microbial inoculants namely, N-fixing bacteria, Bradyrhizobium liaoningense and P-supplying arbuscular mycorrhizal fungus, Ambispora leptoticha on growth and performance of a drought susceptible and high yielding soybean cultivar, MAUS 2 under drought condition.ResultsDrought stress imposed during flowering and pod filling stages showed that, dual inoculation consisting of B. liaoningense and A. leptoticha improved the physiological and biometric characteristics including nutrient uptake and yield under drought conditions. Inoculated plants showed an increased number of pods and pod weight per plant by 19% and 34% respectively, while the number of seeds and seed weight per plant increased by 17% and 32% respectively over un-inoculated plants under drought stress condition. Further, the inoculated plants showed higher chlorophyll and osmolyte content, higher detoxifying enzyme activity, and higher cell viability because of less membrane damage compared to un-inoculated plants under stress condition. In addition, they also showed higher water use efficiency coupled with more nutrients accumulation besides exhibiting higher load of beneficial microbes.ConclusionDual inoculation of soybean plants with beneficial microbes would alleviate the drought stress effects, thereby allowing normal plants’ growth under stress condition. The study therefore, infers that AM fungal and rhizobia inoculation seems to be necessary when soybean is to be cultivated under drought or water limiting conditions.

Comparison in Water Consumption, Plant and Fruit Growth of Different Europe Eggplant Cultivars in Coir Substrate Hydroponics under High Temperature Conditions

This study aims to select eggplant cultivars adaptive to the hot temperature period greenhouse climate by water consumption, and growth performance of plants and fruits of different European eggplant cultivars, including ‘Bartok (BA)’, ‘Bowie (BO)’, ‘Black Pearl(BP)’, ‘Ishbilia (I)’, ‘Mabel (M)’, ‘Vestale (VE)’ and ‘Velia (VL)’, in substrate hydroponic cultivation under hot and humid greenhouse conditions. On the 118 DAT, the leaf number and stem dry weight were highest in ‘VL’, followed by ‘M’, and there was no significant difference in leaf dry weight among cultivars. The marketable fruit number per plant was 16.4 for ‘M’, which was higher than other cultivars, and ‘VE’ and ‘VL’ were 8.5 and 8.8, respectively. The weight per fruit was low for ‘M’ at 136 g, and the highest in ‘VE’ and ‘VL’ at 332 and 281 g, respectively. There was no significant difference in fruit production per plant. In this study, ‘M’, which has high water use efficiency and a large number of fruits, and ‘VL’, which required less quantity to water consumption for producing 200 g of fruit and had a high product weight, will have excellent adaptability in the UAE greenhouse condition.

On Farm Evaluation of Low-Cost Drip Irrigation on Water and Crop Productivity Compared to Conventional Hand Watering System

The efficient use of water is seen as a key to crop production in semi-arid and arid areas of Ethiopia. For smallholder farmers, low-cost drip irrigation systems provide a means of maximizing return on their cropland by increasing the agricultural productivity per unit of land; and through increasing cropping intensity during the dry season. The experiment was conducted in 2019-2020 cropping seasons in moisture deficit areas of Goro district Nere Negaya peasant association (PA), Southeastern Ethiopia. The study was conducted to evaluate and demonstrate low-cost drip irrigation system in moisture deficit areas and increase the productivity of farmers using harvested water with drip irrigation technology. The runoff water during rainy season was collected stored in the lined farm pond (Capacity of 60m3 ) with geomembrane then the water was lifted manually to water tanker for drip. Low-cost drip set which operates with gravity installed at 1m height above the ground level to supply water for the crop was obtained from Maki Batu Farmer Union. The highest Tomato yield of 40.8 t ha-1 which is 64.8% higher over farmer practice was recorded under drip Irrigation with recommended practice at the study area. Whereas Conventional hand watering with recommended management practice gave the Tomato yield of 31.7 t ha-1 (28%) Over farmer practice. The highest water use efficiency(3.76kg/m3) was obtained from Drip Irrigation with recommended managements and saves 10% water over farmer practice and lowest water use efficiency (2.06 kg/m3) was obtained from farmer practice. Consequently, an economic analysis shows that there is a significant difference, in terms of net income, between the various Irrigation method. Tomato was more valuable with Drip Irrigation, compared to hand watering and farmer practice. It can be concluded that Low-cost drip Irrigation with recommended management practice, saves labour and time and it provides uniform irrigation for Tomato production.

Evaluating the effectiveness of different irrigation systems in arid regions: A survey Based Analysis

Low precipitation and high temperatures in arid locations cause a shortage of water supplies and water stress. As it helps maintain and boost crop production, irrigation is an essential tool for agriculture in these areas. However, in arid areas, the efficacy of various irrigation techniques might vary greatly. The purpose of this essay is to assess the efficacy of various irrigation techniques in arid areas, such as conventional surface irrigation, drip irrigation, and spray irrigation. In arid areas, surface irrigation is the most popular type of irrigation, when water is applied to the soil's surface through ditches or furrows. Although this technique is straightforward and low-cost, water losses from evaporation and runoff may happen, leading to inefficient water use and poor crop output. By using a system of pipes and emitters, drip irrigation, on the other hand, feeds water directly to plant roots. Higher water use efficiency and crop yields are the results of this system's reduced water losses and accurate water distribution to the plants.

Rooting depth and water use of summer cover crops in a semi-arid cropping environment

Summer cover crops could add biomass (groundcover), fix nitrogen (legumes) and create biopores in Mediterranean-type cropping systems, but soil water use, especially from the subsoil, may reduce yields of the following winter cash crop. Research on rooting patterns/depth of summer cover crops and consequences for soil moisture storage in Mediterranean-type cropping systems is limited. To assess the rooting patterns and water use of a range of legume (sunn hemp, cowpea, mung bean, lablab), non-legume broadleaf (buckwheat, radish) and cereal (millet) summer cover crops in a Mediterranean-type environment, two field trials (2020 and 2021) and one glasshouse experiment were conducted. Root distribution, rooting depth, root diameter, water use and shoot biomass were evaluated. Millet produced the most biomass of any single species in the field (around 4 t ha-1) and had significantly higher water use efficiency (8.4 g L-1) than all legumes (4–6 g L-1). Millet and buckwheat exhibited dense, shallow root systems that exploited water in the profile surface, while legumes, particularly cowpea, had greater root density in the subsoil, resulting in greater subsoil water use. All legumes had significantly greater average root diameter (0.5–0.7 mm) below 40 cm than millet, buckwheat and radish (0.2–0.4 mm). Dual species mixes with millet or cowpea generally led to increased biomass production and increased rooting and water use in deeper soil layers compared to single species cover crops. The results suggest that millet may be preferable in seasons where the key objective of a summer cover crop is to provide ground cover with minimal water use, whereas in wetter seasons, legumes may be beneficial in drying the subsoil and potentially creating biopores. Ultimately, all cover crops significantly reduced stored soil water compared to a chemical fallow, which will likely affect cash crop yield in many seasons.

Drought stress triggers alterations of adaxial and abaxial stomatal development in basil leaves increasing water-use efficiency.

The physiological control of stomatal opening by which plants adjust for water availability has been extensively researched. However, the impact of water availability on stomatal development has not received as much attention, especially for amphistomatic plants. Therefore, the acclimation of stomatal development in basil (Ocimum basilicum L.) leaves was investigated. Our results show that leaves developed under water-deficit conditions possess higher stomatal densities and decreased stomatal length for both the adaxial and abaxial leaf sides. Although the stomatal developmental reaction to water deficit was similar for the two leaf surfaces, it was proven that adaxial stomata are more sensitive to water stress than abaxial stomata, with more closed adaxial stomata under water-deficit conditions. Furthermore, plants with leaves containing smaller stomata at higher densities possessed a higher water use efficiency. Our findings highlight the importance of stomatal development as a tool for long-term acclimation to limit water loss, with minimal reduction in biomass production. This highlights the central role that stomata play in both the short (opening) and long-term (development) reaction of plants to water availability, making them key tools for efficient resource use and anticipation of future environmental changes.

Invasive microstegium vimineum (Japanese stiltgrass) hinders growth and biomass of hardwood seedlings regardless of light and moisture regime

Limited natural oak (Quercus spp.) regeneration in current-day, closed-canopy upland oak forests across the eastern and central United States has prompted increased use of various silvicultural practices, including prescribed fire and/or thinning, to reduce competition from shade-tolerant, often fire-sensitive species, and ultimately, restore and/or maintain oak landscapes. However, these practices create disturbances that can promote the spread of invasive plants and complicate oak restoration attempts, especially if invasion differentially impacts oaks compared to competitor species during early seedling development. To evaluate if Japanese stiltgrass (Microstegium vimineum (Trin.) A. Camus), an invasive C4 grass common in the understory of these systems, impacts growth and biomass of hardwood seedlings in different light and moisture environments, we established a shadehouse experiment in May 2020 with one-year old seedlings of white oak (Quercus alba L.) and two competitor species, red maple (Acer rubrum L.) and sweetgum (Liquidambar styraciflua L.), in the following treatments: M. vimineum (MV) presence (with/without), light (40/10 % full irradiance), soil moisture (high/low), and their interactions. Monthly, from May to October 2020, we measured seedling height growth, stem basal diameter, and MV cover and height if present. In October 2020, we harvested a subset of seedlings and measured their above- and belowground biomass and aboveground MV biomass when present. At study cessation, regardless of light or moisture treatment, red maple and sweetgum were significantly shorter when grown with MV (17.9 and 15.6 cm, respectively) than without MV (33.5 and 22.3 cm, respectively) and had smaller basal diameters (with MV: 1.03 and 0.94, respectively; without MV: 1.34 and 1.25 cm, respectively) and ∼ two times less biomass. White oak basal diameter was 1.2 times lower with MV (0.77 cm) compared to without MV (0.93 cm), but MV had no impact on white oak height growth or biomass, likely because of its conservative growth strategy and high-water use efficiency. Light and moisture treatments had little impact on MV height and cover, but MV biomass was greater with high (462 dry wt m−2) compared to low (398 g dry wt m−2) moisture treatment and ∼ 1.3 times greater when grown without vs with tree competition. Thus, MV invasion into closed-canopy upland oak forests may have species-specific effects on early seedling growth, reducing growth of competitor seedlings with non-conservative growth strategies more than that of upland oaks, but long-term studies are needed to better understand the potential legacy effects of MV on growing conditions and tree regeneration.

Specific Sound Frequency Improves Intrinsic Water Efficiency in Rice Leaf by Imparting Changes in Stomatal Dimensions

Various attempts have been made to increase rice production, including breeding for high-yielding and stress-tolerant varieties, a good crop management system, and increased agricultural input in rice production. Soundwave stimulation has been demonstrated to affect plant growth; thus, this method can be employed in the current rice production methods to improve yield. The study aims to determine the effects of different sound wave qualities on the general growth, physiological, and morphological of rice seedlings. Rice seeds of the MR219 variety were grown under a glasshouse condition in a nested design with five replications and were stimulated with various sound wave frequencies. Various sound wave frequencies, 380, 359, 357, 353, and 350 Hz, were obtained by placing the pot at varying distances (80, 160, 240, 320, and 400 cm, respectively) from the sound source, except control treatment. There were significant effects in some of the parameters: plant height, leaf physiology, and stomatal pore and length when treated with varying sound wave qualities. Plants can be stimulated with 380, 357, and 350 Hz soundwaves frequencies for the best photosynthetic experience. In addition, 359 Hz of sound wave stimulation resulted in high water use efficiency, which is beneficial in improving crop performance in drought conditions. Thus, it was demonstrated that the sound wave stimulation method has the potential to enhance rice performance in addition to the regular agronomic practices of rice production in farmers’ fields.

Physiological and morphological responses of two beans common genotype to water stress at different phenological stages

Comprehension of the bean responses of beans common under to water deficit is an important tool in agricultural planning, like sowing time, and deficit irrigation management strategies. The study aimed to understand the morpho-physiological responses and yield attributes of two common bean genotypes submitted to water stress at different phenological stages. The study was carried out in a greenhouse, in randomized block scheme with five repetitions. To achieve the objectives deficit irrigation of 25% of crop evapotranspiration was practiced during vegetative (DI-V), flowering (DI-F), and pod filling (DI-PF) stages. A non-deficit irrigated (NDI) and deficit irrigated through vegetative to pod filling stages (DI-VP) treatments were added for comparison. The following morphophysiological responses and yield attributes were evaluated: net assimilation of CO2, stomatal conductance, and leaf transpiration, chlorophyll index, number of trifoliate leaves, chlorophyll index, leaf area, number of grains per plant, number of grains per pod, number of pods per plant, the mass of thousand grains, harvest index, and water use efficiency. The beans genotype under DI-V exhibited acclimation, observed by the relative increment with NDI of 195%, 759%, and 231% of net assimilation of CO2, stomatal conductance, and leaf transpiration, respectively. Plants under treatment DI-PF experienced dis-stress and plastic responses as leaf losses and exhaustion of gas exchanges. Treatment DI-V received 11% less water than NDI and exhibited equal yield, resulting in higher water use efficiency. Yield attributes correlations indicated that yield penalty might be related to pods abortion, which not occurred to plants under DI-V.

Unraveling genetic variation among white spruce families generated through different breeding strategies: Heritability, growth, physiology, hormones and gene expression.

Tree improvement programs select genotypes for faster growth, at both early and late stages, to increase yields over unimproved material, and the improvement is frequently attributed to genetic control in growth parameters among genotypes. Underutilized genetic variability among genotypes also has the potential to ensure future gains are possible. However, the genetic variation in growth, physiology and hormone control among genotypes generated from different breeding strategies has not been well characterized in conifers. We assessed growth, biomass, gas exchange, gene expression and hormone levels in white spruce seedlings obtained from three different breeding strategies (controlled crosses, polymix pollination, open pollination) using parents grafted into a clonal seed orchard in Alberta, Canada. A pedigree-based best linear unbiased prediction (ABLUP) mixed model was implemented to quantify variability and narrow-sense heritability for target traits. The levels of several hormones and expression of gibberellin-related genes in apical internodes were also determined. Over the first two years of development, the estimated heritabilities for height, volume, total dry biomass, above ground dry biomass, root:shoot ratio and root length, varied between 0.10 and 0.21, with height having the highest value. The ABLUP values showed large genetic variability in growth and physiology traits both between families from different breeding strategies, and within families. The principal component analysis showed that developmental and hormonal traits explained 44.2% and 29.4% of the total phenotypic variation between the three different breeding strategies and two growth groups. In general, controlled crosses from the fast growth group showed the best apical growth, with more accumulation of indole-3-acetic acid, abscisic acid, phaseic acid, and a 4-fold greater gene expression of PgGA3ox1 in genotypes from controlled crosses versus those from open pollination. However, in some cases, open pollination from the fast and slow growth groups showed the best root development, higher water use efficiency (iWUE and δ13C) and more accumulation of zeatin and isopentenyladenosine. In conclusion, tree domestication can lead to trade-offs between growth, carbon allocation, photosynthesis, hormone levels and gene expression, and we encourage the use of this phenotypic variation identified in improved and unimproved trees to advance white spruce tree improvement programs.

Residential Water Conservation and the Rebound Effect: A Temporal Decomposition and Investigation

AbstractWater conservation in California has been a major subject of concern for agencies in their efforts to satisfy their residential demand while coping with frequent shortfalls, especially in periods of drought. During the 2012–2016 severe drought in California, the state enacted a conservation mandate that imposed specific conservation targets of 4% up to 36% for water utilities. While the utilities met those targets in 2015, water use, on average, has slowly crept up or rebounded subsequently, although not to pre‐drought levels. Understanding the manner and degree to which water use rebounds can be critically important for water utilities in their planning and investment decisions. Using a unique panel dataset on single‐family residential water use by nearly 20,000 customers of a Northern California water agency from 2013 to 2019, this paper explores the magnitude and character of the rebound effect that occurred after the cessation of a statewide conservation mandate that was imposed on water use in response a severe drought enveloping California from 2014 through 2016. Our results suggest the presence of a significant rebound in water use—of approximately 9% on average—after the conservation mandate ended. Yet, and novel to our research, we find significant heterogeneity in the rebound effects across seasons and water users, with a greater rebound in the warm season months relative to other months and among lower water use households relative to higher water use households. Our results also suggest a significant shift in water use to earlier periods of the day once the mandate was lifted. Understanding the magnitude and variation in rebound effects both temporally and across different types of water users can be useful to water agencies in their efforts to make informed decisions surrounding investments, management, and messaging in response to drought, conservation, and water scarcity.

High resolution annual irrigation water use maps in China based-on input variables selection and convolutional neural networks

Water use and available water resources are the prerequisites for optimal water resources allocation, which is an efficient way to alleviate water scarcity all over the world. However, the spatial scales of water use and available water resources are often not matched due to their different ways for data surveying or observing. The spatial distributed (grid-scale) water use map is one of the ways to convert the spatial scales of the water use and available water resources. As irrigation is essential to guarantee sustainable development of agriculture, food security and economy, and accounts for most water use in China. A framework to generate high resolution (1 km) annual irrigation water use maps has been proposed. An iterative input variables selection (IIS) algorithm is adopted to select the optimal input variables among candidate input variables. After determining the optimal input variables, the convolutional neural network (CNN) is built to establish the relationship between the selected input variables and the irrigation water use. The spatial distributed irrigation water use maps can be produced by the trained CNN with the selected input variables at grid scale. The spatial distributed annual irrigation water use maps in China is produced at 1 km resolution from 1998 to 2013, and the performance of the framework has been proven to be credible with three metrics (i.e., root mean squared error, Nash Sutcliffe efficiency coefficient and relative error). Based on the spatial distributed annual irrigation water use maps, the spatial autocorrelation of annual irrigation water use in China is weak and the clustered pattern is random with 99% confidence. The temporal changing pattern mainly depends on precipitation and soil moisture in most prefectures, and the change of the cultivated area can also lead to dramatic change of the annual irrigation water use in China. The proposed framework can generate high resolution spatial distributed annual irrigation water use maps at grid scale, and the maps can be applied to ensure the optimal water resources allocation to realize efficient utilization of water resources and the agricultural policy-making.

Decomposition of contribution to runoff changes and spatial differences of major tributaries in the middle reaches of the Yellow River based on the Budyko framework

Abstract Quantitative differentiation of climate and human activities on runoff is important for water resources management and future water resources trend prediction. In recent years, runoff in the middle reaches of the Yellow River (MRYR) has decreased dramatically. Many studies have analyzed the causes of runoff reduction, but there is still a lack of understanding of the spatial differences in runoff contributions and their causes. Therefore, this study quantitatively distinguishes the contributions of climate and human activities to runoff changes in nine sub-basins of the MRYR based on the Budyko framework and analyses the differences in the contributions of different basins and their causes. The results show that the runoff in the nine sub-basins decreases significantly and the precipitation increases from northwest to southeast. The contribution of human activities to runoff is greater than that of climate change, especially in the Huangfuchuan (HF) River and Kuye (KY) River basins, where the contribution of human activities to runoff exceeds 90%. The greater impact of human activities in HF River and KY River is due to the significantly higher water use growth rate and normalized vegetation index trends than in other areas.

Effect of proline and humic acid application in salinity stress mitigation on some vegetables in hydroponics

The research aimed to find suitable solutions to reduce the salinity stress of irrigation water for some types of vegetables in hydroponics under two drip and mist irrigation systems. The different concentrations of NaCl for irrigation water, are 500, 1000, 2000, 3000, and 4000 ppm used. Proline (30 mg∙dm –3), humic acid (300 mg∙dm –3) and compared without any from them were used to study their effect on the yield, and water use efficiency. The results indicated that the highest spinach and courgette yield (4.657 and 5.153 kg∙m –2) was observed for the DP500 treatment, and the lowest yield (0.348 and 0.634 kg∙m –2) was observed for the SW4000 treatment, respectively. The use of humic acid led to an increased yield on average by about 16.8 and 19.3% for spinach, and 39.4 and 51.7% for courgette, under drip and mist irrigation, respectively. Using proline led to an increased average yield of about 32.9 and 33% for spinach, and 51.8 and 58.4% for courgette, under drip and mist irrigation, respectively. The highest water use efficiency (WUE) of spinach and courgette (43.1 and 51.5 kg∙m –3) was observed for the DP500 treatment, and the lowest (3.2 and 6.3 kg∙m –3) was observed for the SW4000 treatment. According to our study, the use of proline and humic acid could compensate for the adverse effects of salinity under mist spraying more than drip irrigation.