Daily Water Use Research Articles

Water budget and run‐off response of a tropical multispecies “reforest” and effects of typhoon disturbance

AbstractTo examine claims that reforesting degraded Imperata grassland in Leyte (Philippines) made streamflow perennial again, we studied the hydrological behaviour of a 23‐year‐old mixed‐species “reforest” between June 2013 and May 2014. Typhoon Haiyan, one of the strongest events ever, caused major damage to the site in November 2013. Average daily apparent water use (ET) was 5.0 mm day−1 pretyphoon and 3.2 mm day−1 after disturbance. Corresponding ratios of period total quickflow Qq to precipitation were 16% and 44%. Quickflow volume and peak discharge increased rapidly once a threshold value of ~250 mm for soil water storage in the top 60 cm was exceeded. Before disturbance, quickflow consisted predominantly of lateral subsurface flow due to high soil hydraulic conductivities down to 60 cm. After disturbance, shallow groundwater rose regularly to within 10 cm of the surface on foot slopes, and saturation overland flow was observed during several large storms. Comparing estimated annual ET and Qq for undisturbed conditions for the reforest and a nearby degraded Imperata grassland microcatchment suggested that the extra infiltration following reforestation (~240 mm year−1) exceeded the extra ET by the reforest (100–185 mm year−1), implying a net positive trade‐off (55–140 mm year−1) and tentatively confirming local claims of improved dry‐season flow.

Water education in school curricula: impact on children knowledge, attitudes and behaviours towards water use

At present, there are alarming reports raising serious concerns about water availability in many countries including Morocco. In this context of water scarcity and increasing water demand, education may play a crucial role in transforming values and habits that promote a sustainable management of the resource. Therefore water education topics should be incorporated in school curricula. The first objective of the present study was to explore the status of water education in Moroccan curricula designed for Primary and Lower Secondary School levels. The second objective consisted in assessing students’ knowledge, attitudes and behaviour regarding water-related issues. The study results showed that water-related topics are incorporated in the curricula with multi and interdisciplinary approaches and the most involved are Sciences and Geography; however there is a lack of field and extracurricular activities. While students’ attitudes towards water were positive, their daily water use habits did not match attitudes. To make curricula more effective in changing students’ attitudes and behaviour regarding water use and conservation, water-topics should be taught in accessible ways using values-driven education and innovative methods, field trips and school life activities.

Hydraulic redistribution and its contribution to water retention during short-term drought in the summer rainy season in a humid area

Hydraulic redistribution (HR) in sites with shallow soils and its response to random droughts during the summer rainy season in humid areas remains poorly understood. We investigated the soil moisture dynamics, HR and water buffer of shallow soils by monitoring the soil moisture content at multiple depths during a random drought event in the summer rainy season, in typical forestland and orchard in a subtropical area. Soil moisture sensors were installed at depths of 5, 10, 15, 20 and 30 cm at three sites (forest, peach1, and peach2). The total and net daily water use and water buffer capacity of the root zone were defined and calculated. During the short-term drought, the HR of soil moisture occurred at all sites, suggesting that it could be an important process in both forest and orchard land in response to short-term drought. HR occurred at both daily and multiple-day timescales in the shallow soils. The net daily water use had less difference between the sites than the total daily water use. Principal component analysis of the total and net daily water use showed only evident clustering characteristics for the total daily water use, indicating an important plant-soil interaction effect. The depth-averaged magnitude of daily HR varied from 0.385 mm (0.0077 m3 m−3) at the forest site to 0.725 mm (0.0145 m3 m−3) at the peach1 site. The redistributed water replenished over 75% of the water depleted from the shallow soil. In particular, soil moisture was better retained in 15–20 cm root zone than in other soil layers. Furthermore, the water buffer capacity of the forest site was not higher than those of the two peach sites (where land use converted from forest), indicating that land use conversion does not necessarily weaken soil water retention. The study results highlighted that HR has a significant influence on water recharge and water retention in humid area, thus benefiting plant drought tolerance and total water utilization. This study provides more insights to evaluate HR’s effect on water retention and enhance our understanding of HR in shallow soils during random droughts in the summer rainy season in humid areas.

Effects of size and microclimate on whole-tree water use and hydraulic regulation in Schima superba trees.

BackgroundPlant-water relations have been of significant concern in forestry and ecology studies in recent years, yet studies investigating the annual differences in the characteristics of inter-class water consumption in trees are scarce.MethodsWe classified 15 trees from a Schima superba plantation in subtropical South China into four ranks using diameter at breast height (DBH). The inter-class and whole-tree water use were compared based on three parameters: sap flux density, whole-tree transpiration and canopy transpiration over two years. Inter-class hydraulic parameters, such as leaf water potential, stomatal conductance, hydraulic conductance, and canopy conductance were also compared.Results(1) Mean water consumption of the plantation was 287.6 mm over a year, 165.9 mm in the wet season, and 121.7 mm in the dry season. Annual mean daily water use was 0.79 mm d−1, with a maximum of 1.39 mm d−1. (2) Isohydrodynamic behavior were found in S. superba. (3) Transpiration was regulated via both hydraulic conductance and stoma; however, there was an annual difference in which predominantly regulated transpiration.DiscussionThis study quantified annual and seasonal water use of a S. superba plantation and revealed the coordinated effect of stoma and hydraulic conductance on transpiration. These results provide information for large-scale afforestation and future water management.

Optimising a sensor-based irrigation protocol for a large-scale cut-flower operation in southern California

A network of wireless cellular nodes (EM50G, Meter-Group, Inc., Pullman, USA) and sensors have been deployed at Mellano and Company in Oceanside, CA, to provide managers with soil moisture (volumetric water content, VWC) and electrical conductivity (EC) data, to aid in day-to-day irrigation and salinity management decisions. The primary objective was to achieve a mandated 25% cut in water use without affecting the yield or quality of various cut-flower crops, many of which are grown in long-lived (4-7 year) perennial blocks. Data from 15 nodes/sensors in eight different crops and fields are logged every 15 min from GS1 (VWC) and GS3 (EC) sensors and transmitted by EM50G nodes to a cloud server, up to six times day-1. All data are integrated into a graphical database program (Sensorweb(TM), Mayim, LLC), which is accessible to anyone with an internet connection and access to the password protected website for the company. To rationalize the information that the growers receive, a standardized installation protocol was implemented. Firstly, a combination of VWC and EC sensors are placed at two depths (typically 15 and 30 cm) in the crop rooting zone (influenced by crop development and longevity), to quantify how soil moisture is influenced by daily crop water use. The intent is to actively manage irrigations without significant leaching, except when salts become excessive. Secondly, the specific field capacity (FC) for each field is derived from in situ data, to provide the upper threshold for irrigation, to avoid excessive irrigation durations. A specific threshold VWC for irrigating each crop and soil type is calculated (typically 20% of FC), to provide irrigation managers with a measure of readily-available water. Threshold soil VWC alerts for each block are then created in Sensorweb(TM); the system texts/emails the irrigation manager when that set-point VWC is reached. In this manner, growers are able to fine tune irrigation frequency and duration events (to not exceed FC and increase leaching), to match daily plant water use and crop development over the season. Water savings of about 40% were achieved with Solidago in 2015, and 50-60% for myrtle through the fall/winter of 2015. In this way, Mellano and Company has been able to achieve their targeted irrigation reductions, without compromising crop yield or quality.

Growth and Transpiration Responses of Elephantgrass and Energycane to Soil Drying

ABSTRACTElephantgrass (Pennisetum purpureum Schum.) and energycane (Saccharum spp.) are promising perennial bioenergy crops in the southeastern United States. Despite plentiful rainfall in this region, these perennial grasses have a long growing season and are subject to intermittent drying cycles frequently during summer and fall, yet there is little information on their response to intermittent drought stress. The objectives of this study were to investigate water relations of elephantgrass and energycane genotypes under optimal water inputs and in response to progressive soil drying. Three elephantgrass genotypes (‘UF‐1’, ‘Merkeron’, and ‘PI‐300086’) and three energycane genotypes (‘L79‐1002’, ‘US84‐1047’, and ‘875‐3’) were grown in a greenhouse. Under well‐watered conditions, elephantgrass and energycane exhibited similar daily and total water use, but energycane possessed greater average daily transpiration per unit leaf area (EAVE,leaf) and lower shoot transpiration efficiency (TEshoot) than elephantgrass. Consistent with EAVE, leaf, energycane demonstrated higher stomatal conductance than elephantgrass, but lower assimilation to transpiration ratio (A/T). Among all genotypes, UF‐1 elephantgrass exhibited relatively high A/T, shoot mass production, and TEshoot. In response to progressive soil drying, elephantgrass genotypes closed their stomata at a lower fraction of transpirable soil water and produced higher shoot mass during the drying cycle than energycane genotypes. The different plant water use patterns indicated a species difference in the sensitivity to mild drought stress and could be correlated with their stomatal density and size. The results from this study indicated that elephantgrass is more suited to the frequent mild drought stress between rainfall events common during summer in the southeastern United States.

A methodology for synthetic household water consumption data generation

In the smart cities context, real-time knowledge of residential water consumption has become increasingly important, especially given the fast evolution of sensors, ICT and the production of big, high-resolution data coming from the urban environment. A variety of reasons often leads to the creation of continuity gaps in these data series, thus making the need for a methodology that produces reliable and realistic synthetic data urgent. In this article, we present a methodology that generates synthetic household water consumption data; we showcase it in two case studies, Skiathos, Greece and Sosnowiec, Poland, which exhibit significant differences in water consumption patterns. The methodology captures the stochasticity of daily residential water use. Algorithm validation is implemented through the comparison of various metrics for actual and generated data; this way, we show that the suggested approach is capable of adequately simulating water consumption in both micro- and macro-time scale.

Increased contribution of wheat nocturnal transpiration to daily water use under drought.

Increasing evidence suggests that in crops, nocturnal water use could represent 30% of daytime water consumption, particularly in semi-arid and arid areas. This raises the questions of whether nocturnal transpiration rates (TRN ) are (1) less influenced by drought than daytime TR (TRD ), (2) increased by higher nocturnal vapor pressure deficit (VPDN ), which prevails in such environments and (3) involved in crop drought tolerance. In this investigation, we addressed those questions by subjecting two wheat genotypes differing in drought tolerance to progressive soil drying under two long-term VPDN regimes imposed under naturally fluctuating conditions. A first goal was to characterize the response curves of whole-plant TRN and TRN /TRD ratios to progressive soil drying. A second goal was to examine the effect of VPDN increase on TRN response to soil drying and on 13 other developmental traits. The study revealed that under drought, TRN was not responsive to progressive soil drying and-intriguingly-that TRN seemingly increased with drought under high VPDN consistently for the drought-sensitive genotype. Because TRD was concomitantly decreasing with progressive drought, this resulted in TRN representing up to 70% of TRD at the end of the drydown. In addition, under drought, VPDN increase was found not to influence traits such as leaf area or stomata density. Overall, those findings indicate that TRN contribution to daily water use under drought might be much higher than previously thought, that it is controlled by specific mechanisms and that decreasing TRN under drought might be a valuable trait for improving drought tolerance.

Subsurface water-use strategies and physiological responses of subtropical eucalypt woodland vegetation under changing water-availability conditions

This study investigated subsurface water-use strategies and physiological responses of subtropical remnant eucalypt woodlands in south-eastern Queensland, Australia. A land surface temperature (LST) model-data approach was used to detect daily use of subsurface water (i.e. soil moisture obtained from depths >30cm and aquifer groundwater) by woody vegetation to a confidence level of 95%. Vegetation subsurface water use was quantified over a 13-year period (2000–2012) coinciding with a series of wet and dry climatic periods. Land surface temperature and subsurface water use time-series data were compared to local meteorological (vapour pressure deficit, rainfall, and soil water availability) and vegetation (leaf area index, stomatal resistance and latent heat loss) data to determine vegetation strategies to declining shallow (<30cm depth) soil water availability. Different vegetation subsurface water-use strategies and physiological response to changes in water availability were identified at inter- and intra-annual time-scales. At the intra-annual scale, frequency of subsurface water use by vegetation was strongly influenced by availability of shallow soil water. From January–September in this landscape, frequency of subsurface water use by vegetation remained relatively constant, supplementing decreasing shallow soil water availability and/or increasing evaporative demand. From October–December, the vegetation opportunistically utilised more abundant shallow soil water arising from more frequent, intense rainfall events, rather than relying on subsurface water. At the inter-annual scale, vegetation increased frequency of subsurface water use and decreased leaf area to reduce latent heat loss in response to dry conditions. Then, during wet years, subsurface water use by vegetation decreased in frequency as water was increasingly sourced from shallow soil layers. However, despite preceding dry periods of different severity, and exhibiting different average annual rainfall, air temperatures and reduction in the frequency of subsurface water use by vegetation, leaf area increased by approximately the same amount for both ‘recovery’ years. This suggests that investment in canopy leaf growth by this vegetation was more sensitive to the onset of increased water availability after drought rather than the overall volume of water made available by rainfall.

Genotypic Variation in Yield, Yield Components, Root Morphology and Architecture, in Soybean in Relation to Water and Phosphorus Supply.

Water shortage and low phosphorus (P) availability limit yields in soybean. Roots play important roles in water-limited and P-deficient environment, but the underlying mechanisms are largely unknown. In this study we determined the responses of four soybean [Glycine max (L.) Merr.] genotypes [Huandsedadou (HD), Bailudou (BLD), Jindou 21 (J21), and Zhonghuang 30 (ZH)] to three P levels [applied 0 (P0), 60 (P60), and 120 (P120) mg P kg-1 dry soil to the upper 0.4 m of the soil profile] and two water treatment [well-watered (WW) and water-stressed (WS)] with special reference to root morphology and architecture, we compared yield and its components, root morphology and root architecture to find out which variety and/or what kind of root architecture had high grain yield under P and drought stress. The results showed that water stress and low P, respectively, significantly reduced grain yield by 60 and 40%, daily water use by 66 and 31%, P accumulation by 40 and 80%, and N accumulation by 39 and 65%. The cultivar ZH with the lowest daily water use had the highest grain yield at P60 and P120 under drought. Increased root length was positively associated with N and P accumulation in both the WW and WS treatments, but not with grain yield under water and P deficits. However, in the WS treatment, high adventitious and lateral root densities were associated with high N and P uptake per unit root length which in turn was significantly and positively associated with grain yield. Our results suggest that (1) genetic variation of grain yield, daily water use, P and N accumulation, and root morphology and architecture were observed among the soybean cultivars and ZH had the best yield performance under P and water limited conditions; (2) water has a major influence on nutrient uptake and grain yield, while additional P supply can modestly increase yields under drought in some soybean genotypes; (3) while conserved water use plays an important role in grain yield under drought, root traits also contribute to high nutrient uptake efficiency and benefit yield under drought.

Irrigation scheduling and soil moisture dynamics influence water uptake by Huanglongbing affected trees

Improved understanding of citrus water use and soil moisture distribution in Huanglongbing (HLB) (Candidatus Liberibacter asiaticus) affected groves is critical for devising appropriate recommendations for optimizing water use and sustaining citrus yields. Thus, a study was conducted to investigate soil moisture movement and water use patterns in central, south-central and southwest Florida. Treatments included: 1) daily irrigation (Daily), 2) University of Florida Institute of Food and Agricultural Sciences recommended scheduling characterized by irrigating every two days to replace water used by crop evapotranspiration (IFAS), and 3) irrigation scheduled half the number of days between irrigation recommended by IFAS and Daily (Intermediate). The total irrigation was designed to meet estimated crop water use (ETc) for mature citrus equaling 1127mm, 1138mm, and 1211mm, and 1211mm per year at Avon Park, Arcadia and Ave Maria, respectively. Field capacities (FC) and available water capacity (AWC) varied between 0.062cm3cm−3 to 0.11cm3cm−3, with AWC estimated to be 86% to 91% of FC. Irrigation set points for irrigation scheduling were estimated at 33 and 50% of allowable soil water depletion (ASWD) and varied between 0.020 and 0.033cm3cm−3 while 50% ASWD varied between 0.031 and 0.050cm3cm−3. Daily water use largely varied between 0.02 and 0.18g/d/cm2 in Summer 2013, 0.01–0.15g/d/cm2 in Fall 2013 and 0.01 and 0.24g/d/cm2 in Spring 2014. Water use pattern was largely of the order Daily>IFAS>Intermediate. Moisture contents were similar among irrigation schedules varying between 5–20%, 1–14% and 5–25% at 15-, 30-, and 45-cm soil depths, respectively, increasing with depth possibly as a result of uptake in the top 30cm. These findings should help in refining limits for available water contents and estimating irrigation water demand to sustain citrus productivity of HLB infected trees.

A preliminary investigation of water usage behavior in single-family homes

As regional drought conditions continue deteriorating around the world, residential water use has been brought into the built environment spotlight. Nevertheless, the understanding of water use behavior in residential buildings is still limited. This paper presents data analytics and results from monitoring data of daily water use (DWU) in 50 single-family homes in Texas, USA. The results show the typical frequency distribution curve of the DWU per household and indicate personal income, education level and energy use of appliances all have statistically significant effects on the DWU per capita. Analysis of the water-intensive use demonstrates the residents tend to use more water in post-vacation days. These results help generate awareness of water use behavior in homes. Ultimately, this research could support policy makers to establish a water use baseline and inform water conservation programs.

Determining pomegranate water and nitrogen requirements with drip irrigation

Despite being an ancient crop there is limited knowledge on the water and nitrogen (N) requirements of pomegranate. We conducted research at the University of California, Kearney Agricultural Research and Extension Center (KARE) to determine the water and N requirements of a developing pomegranate orchard. Pomegranate trees (Punica granatum L. var. Wonderful) were planted in 2010. The irrigation treatments were surface drip irrigation (DI) and subsurface drip irrigation (SDI) with three N sub-treatments (N application rates of 50, 100, and 150% of current practice) and 5 replications in split-plot design. A weighing lysimeter located in the experimental field was used to automatically irrigate the orchard after 1.0mm of measured crop water use. The trees received uniform application of fertilizers and water during the first two years of growth to insure uniform stand establishment prior to beginning the experiment. The pH of the irrigation water was maintained at 6.5±0.5 by injection of N as urea sulfuric acid (US-10; 10% N). Differential N treatments were started in 2012 and continued through the end of the project. Phosphorus (PO4–P) was continuously injected during irrigation and potassium (K2T) was injected weekly. We report the results of the study from 2013 to 2015. From 2013 to 2015 the applied N ranged from 62 to 332kg/ha and the total yields ranged from 33,144 to 57,769kg/ha. There were no statistical differences in yield within any year related to total applied N. The yearly applied irrigation water increased as the plant size increased. The total water requirement is approximately 952mm and the maximum daily water use was 10.5mm. The DI irrigation application went from 645mm to 932mm and the SDI application increased from 584mm to 843mm from 2013 to 2015. A fifth order polynomial was fitted to the crop coefficient using the 2015 data. The use of SDI resulted in lower weed pressure in the SDI plots than in the DI irrigated plots in all three years. High frequency irrigation resulted in nitrate being managed within the soil profile to a depth of 1.5 m by minimizing deep percolation losses to the groundwater. While the yields were higher in the SDI than the DI system they were not statistically different. Although there were some differences in N content in tree leaves and fruit peels, there were no differences in fruit arils among N rates. The N requirement is in the range of 62–112kg/ha (109–198g/tree) for a mature pomegranate orchard and will ultimately depend on the planting density.

Evaluating a Physiological-based, On-demand Irrigation System for Container-grown Woody Plants with Different Water Requirements

Two sensor-based irrigation scheduling systems were compared for water use and plant growth in container-grown Green Velvet boxwood (Buxus sempervirens L. × B. microphylla Siebold &amp; Zucc. var. koreana ‘Green Velvet’) and slender deutzia (Deutzia gracilis Siebold &amp; Zucc). These crops were chosen because they have different water requirements during production. The two sensor-based irrigation systems included a physiological-based on-demand (OD) irrigation system where the set point was derived from the relationship between substrate moisture and photosynthetic rate. The second system was a daily water use (DWU) method where the amount of water used by the crop was replaced each day. The objective of the study was to evaluate and compare water use and growth metrics using the OD and DWU irrigation scheduling regimes for two container-grown woody plants that differed in their water consumption. There were no differences in root and shoot biomass or growth index due to the irrigation schedule employed for either boxwood or deutzia. For boxwood plants, OD irrigation reduced water consumption by 35.5% and enhanced water use efficiency (WUE) by 54.5% compared with DWU. Total water use of deutzia in OD zones was reduced by 26.5% compared with DWU. DWU offers the labor scheduling advantage of irrigation occurring at a set time of day, and OD offers the advantage of watering as required, potentially reducing water stress as the season progresses and as the plant size and atmospheric demand increase.

Spatial heterogeneity in stand characteristics alters water use patterns of mountain forests

Mountain landscapes have complex and rugged topographies, with abrupt spatial and temporal changes in microclimate and soil properties, factors that directly affect tree growth and canopy processes. These may alter functional relationships over short spatial scales, rendering the use of allometry in scaling tree water use (TWU) from single trees to stand level less accurate. On the other hand, canopy processes, especially stomatal conductance are sensitive to the environmental conditions prevailing above the canopy. Given that these also change rapidly in a mountain landscape, we speculate that patterns of water use in a complex landscape are determined by the interaction between stand structure and canopy conductance. We examined forest stand structure, microclimate and sap flux density (Js) in two forest stands distributed at 50m and 330m elevations of the Dinghushan Mountain in south China to determine how they influence tree functional allometry for scaling up stand water use. Tree sapwood area (SA) was correlated with the diameter at breast height (DBH) irrespective of species and location within the forest catchment. The maximum sap flux density (Js) on a clear sunny day ranged from 18±9 to 48±12 and 25±8 to 64±11gm−2s−1 in the 330m and 50m forest stands, respectively. Differences among trees and between forest stands were significant (p<0.05). Daily maximum tree water use (TWU) ranged from 2±4 to 36±12kgd−1 and 4±3 to 42±11kgd−1 in the 330 and 50m, respectively. Differences between the stands were significant. Within a stand, TWU was correlated with DBH irrespective of species. This functional relationship was, however, different between the forest stands, resulting in different E estimates for the respective stands. Cross-site variations were due to differences in vapor pressure deficit (VPD), photosynthetic photon flux density (PPFD) and leaf specific canopy conductance (gt). While trees responded in a similar manner to the microclimatic environment, between-site differences in stand characteristics shifted the functional relationships. Thus, in this complex mountain terrain, using a universal, site-specific allometric equation in scaling up sap flow from single trees to catchment-scale can lead up to 30% inaccuracy.

On-Site Wastewater Systems: Investigating Dynamics and Diurnal Patterns Impacting on the Performance of Mound Systems

Many dynamics and diurnal patterns impact upon the performance of effluent disposal areas. The timing of household water use and conveyance to a septic tank impacts on the available volume for application to an effluent disposal area. The timing and method of effluent application will impact on the performance of the effluent disposal area in assimilating nutrients and maintaining adequate infiltration rates. Rainfall patterns will impact on soil saturation at different times during the year; and threshold rainfall events may increase groundwater levels that will impact on the performance of the effluent disposal area. However, the dynamics and diurnal patterns comprising the “whole-of-on-site wastewater- system” are rarely discussed in the literature. This paper uses data obtained from a study of two allotments in a non-sewered subdivision at Salt Ash (NSW) to highlight these dynamics and diurnal patterns in order to improve the performance evaluation of on-site wastewater systems, in particular Mound systems. Results indicate that under existing septic tank-collection well design criteria the variability in average daily indoor water use and average diurnal water use patterns will impact on the temporal comparative performance of effluent disposal areas (Mound systems) at similar sites.

Effects of irrigation regime on canopy water use and dry matter production of ‘Tempranillo’ grapevines in the semi-arid climate of Southern Oregon, USA

Vine water use and dry matter production were measured in a Vitis vinifera L. cv. ‘Tempranillo’ vineyard in Southern Oregon, USA, a semi-arid region. Whole-canopy chambers were custom-built for gas exchange measurements at two phenological stages, pre-véraison and post-véraison, on mature grapevines that were irrigated at three different levels: (i) full irrigation, where 100% of crop evapotranspiration (ETc) was provided (FI); (ii) sustained deficit irrigation, where 50% ETc was provided for the remainder of the season once a specific threshold of vine water status was reached (SDI); and, (iii) regulated deficit irrigation, where 30% ETc was provided once the same threshold was reached until véraison and increased to 50% ETc during the post-véraison to harvest period (RDI). Soil moisture was monitored continuously in all treatments, and vine water status was measured bi-weekly. Despite similar environmental conditions at both timepoints, differences in whole-vine gas exchange were not apparent between irrigation treatments at pre-véraison but were marked post-véraison when vine water status differences were greater. Vine water use and dry matter production were both positively-related to irrigation level. Instantaneous water use efficiency peaked early in the day but was not higher on a daily basis in deficit-irrigated vines likely due to their higher dark respiration rates. Nocturnal transpiration was also positively-related to irrigation level and represented nearly one-third of daily water use in the FI vines but near zero in the RDI vines. These results are discussed in the context of common deficit irrigation scheduling practices in vineyards and shed light on the limitations of ETc-based approaches.

Estimating wasteful water use from car washing points on the water supply system of Yaounde, Cameroon

Regular access to pipe-borne water remains a challenge to urban dwellers in Cameroon in general and those in Yaounde in particular. From that backdrop, this paper estimates the quantity of water used in car washing in the city of Yaounde as a representation of some of the numerous irrational water uses in the city in spite of its scarcity. It argues that the amount of water lost in car washing in the absence of water conservation and recycling techniques can offset the domestic water shortages experienced in many neighbourhoods of Yaounde significantly. To achieve this, both qualitative and quantitative methods were applied. An exhaustive enumeration of car washing points was undertaken in the Yaounde VI subdivision of the city of Yaounde. Water sources were determined and the water quantities used on a daily basis estimated from water bills paid and volumetric capacities of water reservoirs in the washing stations. Car washing was observed to be a streetside activity in dominantly outlying residential areas where some vacant undeveloped land still existed with the CDE being the major water supplier notwithstanding the emergence of alternative sources. Over 198.122 m3 of water (0.2 % of daily water use in the city of Yaounde) was estimated to be consumed by car washing in Yaounde VI. With a huge water supply deficit, of 200,000 m3 on its estimated daily water needs of 311,000 m3, water losses via spillouts from car washing points represents a significant withdrawal from the system that could reduce the daily shortages experienced by numerous households in Yaounde. There is the strong need for a water use policy that internalizes micro water recycling schemes in public water use as a means of reducing water demand, harvesting and wastage.

A new multiple regression model for predictions of urban water use

Shortages of freshwater have become a serious issue in many regions around the world, partly due to rapid urbanisation and climate change. Sustainable city development should consider minimising water use by people living in cities and urban areas. The purpose of this paper is to improve our understanding of water-use behaviour and to reliably predict water use. We collected appropriate data of daily water use, meteorological parameters, and socioeconomic factors for the City of Brossard in Quebec, Canada, and analysed these data using multiple regression techniques. The techniques represent a new approach to predictions of daily water use; its base use component is predicted using a function of socioeconomic factors, as opposed to a function of time as in existing approaches. The quality of the new approach is quantitatively demonstrated. Time series of predicted daily water-use captures observed characteristics very well, and improves the results of the weighted coefficient of determination, the relative index of agreement and the root mean square error from the existing approaches. Water use in the city exhibits a downward trend possibly due to an increasing annual charge for water use. Water use increases due to weekend effect. It decreases in the occurrence of rainfall; the decrease is more sensitive to previous-day than current-day rainfall. The analysis procedures reported in this paper can be applied to analyse water use in any other cities. The new approach would be a useful tool for decision makers to manage water use by adjusting water consumption policies and price.

Temporal dynamics of maize plant growth, water use, and leaf water content using automated high throughput RGB and hyperspectral imaging

Automated collection of large scale plant phenotype datasets using high throughput imaging systems has the potential to alleviate current bottlenecks in data-driven plant breeding and crop improvement. In this study, we demonstrate the characterization of temporal dynamics of plant growth and water use, and leaf water content of two maize genotypes under two different water treatments. RGB (Red Green Blue) images are processed to estimate projected plant area, which are correlated with destructively measured plant shoot fresh weight (FW), dry weight (DW) and leaf area. Estimated plant FW and DW, along with pot weights, are used to derive daily plant water consumption and water use efficiency (WUE) of the individual plants. Hyperspectral images of plants are processed to extract plant leaf reflectance and correlate with leaf water content (LWC). Strong correlations are found between projected plant area and all three destructively measured plant parameters (R2>0.95) at early growth stages. The correlations become weaker at later growth stages due to the large difference in plant structure between the two maize genotypes. Daily water consumption (or evapotranspiration) is largely determined by water treatment, whereas WUE (or biomass accumulation per unit of water used) is clearly determined by genotype, indicating a strong genetic control of WUE. LWC is successfully predicted with the hyperspectral images for both genotypes (R2=0.81 and 0.92). Hyperspectral imaging can be a very powerful tool to phenotype biochemical traits of the whole maize plants, complementing RGB for plant morphological trait analysis.