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1.
Freshwater scarcity is a growing concern, placing considerable importance on the accuracy of indicators used to characterize and map water scarcity worldwide. We improve upon past efforts by using estimates of blue water footprints (consumptive use of ground- and surface water flows) rather than water withdrawals, accounting for the flows needed to sustain critical ecological functions and by considering monthly rather than annual values. We analyzed 405 river basins for the period 1996-2005. In 201 basins with 2.67 billion inhabitants there was severe water scarcity during at least one month of the year. The ecological and economic consequences of increasing degrees of water scarcity--as evidenced by the Rio Grande (Rio Bravo), Indus, and Murray-Darling River Basins--can include complete desiccation during dry seasons, decimation of aquatic biodiversity, and substantial economic disruption. 相似文献
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Soil water availability for plants as quantified by conventional available water, least limiting water range and integral water capacity 总被引:1,自引:0,他引:1
Hossein Asgarzadeh Mohammad Reza Mosaddeghi Ali Akbar Mahboubi Akram Nosrati Anthony Roger Dexter 《Plant and Soil》2010,335(1-2):229-244
There are different approaches to define the soil available water (SAW) for plants. The objectives of this study are to evaluate the SAW values of 12 arable soils from Hamadan province (western Iran) calculated by plant available water (PAW), least limiting water range (LLWR) and integral water capacity (IWC) approaches and to explore their relations with Dexter’s index of soil physical quality (i.e., S-value). Soil water retention and mechanical resistance were determined on the intact samples which were taken from the 5–10 cm layer. For calculation of LLWR and IWC, the van Genuchten-Mualem model was fitted to the observed soil water retention data. Two matric suctions (h) of 100 and 330 cm were used for the field capacity (FC). There were significant differences (P?<?0.01) between the SAW values calculated by PAW100, PAW330, LLWR100, LLWR330 and IWC. The highest (i.e., 0.210 cm3 cm?3) and the lowest (i.e., 0.129 cm3 cm?3) means of SAW were calculated for the IWC and LLWR330, respectively. The upper limit of LLWR330 for all of the soils was h of 330 cm, and that of LLWR100 (except for one soil that was air-filled porosity of 0.1 cm3 cm?3) was h of 100 cm. The lower limit of LLWR330 and LLWR100 for five soils was h of 15,000 cm and for seven soils was mechanical resistance of 2 MPa. The IWC values were smaller than those of LLWR100 for two soils, equal to those of LLWR100 for three soils and greater than those of LLWR100 for the rest. There is, therefore, a tendency to predict more SAW using the IWC approach than with the LLWR approach. This is due to the chosen critical soil limits and gradual changes of soil limitations vs. water content in the IWC calculation procedure. Significant relationships of SAW with bulk density or relative bulk density were found but not with the clay and organic matter contents. Linear relations between IWC and LLWR100 or LLWR330 were found as: IWC?=??0.0514 + 1.4438LLWR100, R 2?=?0.83; and IWC?=??0.0405 + 2.0465LLWR330, R 2?=?0.84, respectively (both significant at P?<?0.01). Significant relationships were obtained between the SAW values and S indicating the suitability of the index S to explain the availability of soil water for plants even when complicated approaches like IWC are considered. Overall, the results demonstrate the importance of the choice of the approach to be used and its critical limits in the estimation of the soil available water to plants. 相似文献
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Jana Pospíšilová 《Biologia Plantarum》1969,11(2):130-138
Intensity of transpiration, intensity of water absorption, water saturation deficit (w.s.d.) in different parts of samples and rate of water transport was investigated in samples from leaf tissue of fodder cabbage and banana-tree. In all experiments (at initial w.s.d. 0% and 20%, in samples from upper, middle and lower leaves of fodder cabbage and from leaves of banana-tree) a distinct gradient of w.s.d. in the direction of transport of water was determined, therefore the limiting factor in the water balance was rate of water transport and not rate of water absorption. The lowest amount of water was always transported within transpiring part of sample. When the initial w.s.d. was 0% not only the water transported by tissue from the environment, but also the water of the leaf tissue itself took part in water lost by transpiration and therefore water stress originated in the whole sample. At an initial w.s.d. of 20%, the rate of water absorption was higher than the rate of water transport and therefore the increase of w.s.d. in the transpiring part of the sample was accompanied by a simultaneous decrease of w.s.d. in the transporting part. An increase in the value of w.s.d. in leaf tissue proportionally increased the resistance of water transport in the liquid phase (on the average from 1·7 . 103 to 6·7 . 103 atm min cm2 g?1) and also in the gaseous phase (on the average from 2·7 . 10?2 to 14·0 . 10?2 min cm?1). It was proved that insufficient rate of water transport can be responsible for the origin of water stress. At the same time the rate of water transport was influenced by the value of the w.s.d. since every change of w.s.d. in leaf tissue not only the gradient of water potential changed but also the resistance to water transport. 相似文献
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PETER CULLEN 《Freshwater Biology》1990,24(1):201-209
SUMMARY. 1. It is common to observe friction between limnologists and the managers of water resources. This is often a result of misunderstandings about the cultures within which each works.
2. There are a number of ways that science can contribute to effective management of water resources, but limnologists must appreciate that there are value questions which are not the sole prerogative of science to answer.
3. Managers often misunderstand science and expect it to deliver a truth that is non-arguable. They fail to understand the very process of science demands no such truths, so that assumptions, methods and conclusions can always be challenged.
4. One way to bridge this boundary is to develop the scientific broking role. Another is to do better and more relevant science. Ways of doing both are discussed. 相似文献
2. There are a number of ways that science can contribute to effective management of water resources, but limnologists must appreciate that there are value questions which are not the sole prerogative of science to answer.
3. Managers often misunderstand science and expect it to deliver a truth that is non-arguable. They fail to understand the very process of science demands no such truths, so that assumptions, methods and conclusions can always be challenged.
4. One way to bridge this boundary is to develop the scientific broking role. Another is to do better and more relevant science. Ways of doing both are discussed. 相似文献
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Relative water content (RWC) and water potential as measuredwith the pressure chamber were evaluated as indicators of waterstatus of tissue-cultured apple shoots and plantlets (shootswith roots). During the hydration required for RWC measurement,both water content and water potential exhibited the same hydrationkinetics, indicating that 10 h were required for full hydration.Once full hydration was reached, shoot mass remained relativelyconstant. Moisture release characteristics were also constructedand the associated shoot and plantlet water relations parameterswere estimated. Underin vitroconditions, both shoot and plantletwater potential were similar to the water potential of the culturemedium in which they were grown. The moisture release characteristicof shoots and plantlets was consistent with that expected fortypical plant tissues, and gave estimates of maximum modulusof elasticity (6.201.14 MPa), osmotic potential at saturation(0.85 0.10 MPa), osmotic potential at zero turgor (1.16 0.14 MPa) and RWC at zero turgor (78 2%) which were similarto values in the literature. Higher values of leaf conductanceand RWC were found in shoots and plantlets placed at 95% RH(21 C) compared to those at 90% RH. Plantlets had higher valuesof both conductance and RWC compared to shoots, suggesting thatinvitroroots are functional in water uptake. Relative water contentwas related to measures of physiological activity such as leafconductance, and it was also easier to measure than water potential.Relative water content is suggested as a sound index of waterstatus in tissue culture plants. Key words: Conductance, microculture, water status, water stress. 相似文献
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Abstract. Wphen there is no external source of water, plants can grow by mobilizing internal water from nongrowing tissues. We investigated how this internal water moves by measuring continuously and simultaneously the water potential (ψw ) of soybean ( Glycine max L. Merr.) seedlings in the upper, growing stem tissues and the lower, non-growing stem tissues. When external water was available to the roots, the stems grew rapidly and the ψw of the growing tissue was continually below that of the nongrowing tissue and the medium around the roots. This indicated that a growth-induced gradient in ψw favoured water movement from the external source to the growing cells. When the external source was removed, the ψw of the growing tissue remained constant for a time and the ψw of the nongrowing tissue decreased somewhat. Growth took place slowly as water was withdrawn from the nongrowing tissue but ψw gradients continued to favour water transport to the growing cells. On the other hand, if this internal source was removed by excision, growth ceased abruptly. In this case, the cell walls relaxed and the ψw of the growing tissue decreased by about 0.1 MPa instead of remaining constant. The ψw of the detached nongrowing tissues remained constant instead of decreasing. This indicates not only that water mobilization required attached nongrowing or slowly growing tissues but also that mobilization affected wall relaxation. Thus, ψw differences may mobilize internal water, may explain the continued growth of plants and plant parts removed from external sources of water, and may account for discrepancies in measurements of cell wall properties in growing tissues. 相似文献
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B. H. Junker M. Stanik J. Adamca K. LaRiviere M. Abbatiello P. Salmon 《Bioprocess and biosystems engineering》1997,17(5):277-286
An ambient loop USP purified water system has been designed and implemented using carbon and ion exchange resin beds, ultraviolet light systems and polishing filters to produce water consistently meeting or exceeding all USP XXIII quality specifications for purified water. The circulation system is constructed of PVDF plastic piping material installed in a continuous fully-drainable loop. The system was sized for a pilot scale fermentation/harvest process at the 1000?l cultivation scale. This system passed all installation and operational qualification testing as well as sixty days of continuous performance qualification testing before entering into an ongoing monitoring regimen. Excursions outside acceptable water quality parameters during this extensive monitoring regimen were minimal. Sanitization of the system, along with bed and filter changes at the time of sanitization, was conducted every 3 to 6 months to insure consistent water quality. 相似文献
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Veera Gnaneswar Gude 《Reviews in Environmental Science and Biotechnology》2017,16(4):591-609
The act of ensuring freshwater is considered the most essential and basic need for humanity. Although the planet is water-rich in some terms, the freshwater sources available for human consumption and beneficial uses are very limited. Excess population growth, industrial development coupled with improving living standards have caused an unprecedented need for freshwater all over the world. Regions once rich in water resources are struggling to meet the ever increasing demands in recent years. In addition, climate change and unsustainable management practices have led to a situation called “drought” in many regions. Water supplies in drought conditions can be addressed by taking two major approaches related to management and technology development. The management approaches include demand mitigation and supply enhancement. Demand mitigation can be done by implementing water conservation practices, and by enforcing a mechanism to influence user-responsible behavior through higher water fares and other billing routes. Supply enhancement can be achieved by utilizing the methods available for water reclamation, reuse and recycle including rain harvesting. This paper provides a critical insight of the causes for drought and the issues caused by persistent drought conditions followed by discussion of management and technological approaches required to maintain adequate water resources around the world. Challenges and opportunities involved in implementation of desalination and water reuse technologies in addressing global water scarcity are discussed in detail with case studies 相似文献
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Modeling soil water movement with water uptake by roots 总被引:16,自引:0,他引:16
Soil water movement with root water uptake is a key process for plant growth and transport of water and chemicals in the soil-plant
system. In this study, a root water extraction model was developed to incorporate the effect of soil water deficit and plant
root distributions on plant transpiration of annual crops. For several annual crops, normalized root density distribution
functions were established to characterize the relative distributions of root density at different growth stages. The ratio
of actual to potential cumulative transpiration was used to determine plant leaf area index under water stress from measurements
of plant leaf area index at optimal soil water condition. The root water uptake model was implemented in a numerical model.
The numerical model was applied to simulate soil water movement with root water uptake and simulation results were compared
with field experimental data. The simulated soil matric potential, soil water content and cumulative evapotranspiration had
reasonable agreement with the measured data. Potentially the numerical model implemented with the root water extraction model
is a useful tool to study various problems related to flow transport with plant water uptake in variably saturated soils.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Inferring foliar water uptake using stable isotopes of water 总被引:1,自引:0,他引:1
A growing number of studies have described the direct absorption of water into leaves, a phenomenon known as foliar water uptake. The resultant increase in the amount of water in the leaf can be important for plant function. Exposing leaves to isotopically enriched or depleted water sources has become a common method for establishing whether or not a plant is capable of carrying out foliar water uptake. However, a careful inspection of our understanding of the fluxes of water isotopes between leaves and the atmosphere under high humidity conditions shows that there can clearly be isotopic exchange between the two pools even in the absence of a change in the mass of water in the leaf. We provide experimental evidence that while leaf water isotope ratios may change following exposure to a fog event using water with a depleted oxygen isotope ratio, leaf mass only changes when leaves are experiencing a water deficit that creates a driving gradient for the uptake of water by the leaf. Studies that rely on stable isotopes of water as a means of studying plant water use, particularly with respect to foliar water uptake, must consider the effects of these isotopic exchange processes. 相似文献
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N. F. Low 《Hydrobiologia》1982,88(1-2):93-101
The options available for the management of Rutland Water are identified and their use discussed. The changes in the chemistry of the stored water with regard to sulphate, silica (molybdate-reactive), dissolved reactive phosphate and total oxidised nitrogen are shown. 相似文献
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Rates of weight loss and release of nutrients during different phases of decomposition in young water hyacinth leaves were
determined under laboratory conditions. The leaves decomposed solely by physical leaching during the initial 4-day phase and
later by microbial processes. The largest part of weight loss and nutrient release by physical leaching took place within
the first 4 h of incubation and thereafter the decomposition rate declined. Microbial processes decayed leaves at a significantly
higher rate than that by physical leaching. The overall decay rate constants were related inversely and the release of nutrients
directly to the levels of leaf additions in the lake water. The dissolved inorganic and organic nutrients were released chiefly
by abiotic processes during the initial as well as later phases of decay. The release was significantly higher during the
initial phase in comparison with that during the later phase. Microbes utilized only a small amount of nutrients that were
released during decomposition of water hyacinth leaves. The % release of various elements from the decaying leaves was in
the order of K > P > C > Na > N. 相似文献
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Decomposition of water hyacinth detritus in eutrophic lake water 总被引:1,自引:1,他引:0
A study was conducted to determine the seasonal production of detritus by water hyacinths [Eichhornia crassipes (Mart.) Sohns] cultured in eutrophic Lake Apopka water, and the decomposition of detritus in situ and under laboratory conditions. Annual averages for C, N and P deposited through detritus production at the sediment-water interface were 2870, 176 and 19 kg ha-1 yr-1, respectively.Decomposition rates were faster in the root zone of hyacinth mats than at the sediment-water interface. Approximately 92% of the detritus C deposited at the sediment-water interface was decomposed in one year, while only 11% of the detrital organic N was mineralized. Detrital tissue gained P during decomposition, suggesting P limitation for the system. Dry-weight loss of detrital tissue was significantly correlated with the mass of C lost (r
2 = 0.947**), C/N ratio (r
2 = 0.644**) and C/P ratio (r
2 = 0.428**).Florida Agricultural Experiment Stations Journal Series No. R-00348. 相似文献
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Visser GH Dekinga A Achterkamp B Piersma T 《American journal of physiology. Regulatory, integrative and comparative physiology》2000,279(5):R1795-R1804
We investigated the applicability of (2)H to measure the amount of body water (TBW) and water fluxes in relation to diet type and level of food intake in a mollusk-eating shorebird, the Red Knot (Calidris canutus). Six birds were exposed to eight experimental indoor conditions. Average fractional (2)H turnover rates ranged between 0. 182 day(-1) (SD = 0.0219) for fasting birds and 7.759 day(-1) (SD = 0.4535) for birds feeding on cockles (Cerastoderma edule). Average TBW estimates obtained with the plateau method were within the narrow range of 75.9-85.4 g (or between 64.6 and 70.1% of the body mass). Those obtained with the extrapolation method showed strong day-to-day variations (range 55.7-83.7 g, or between 49.7 and 65.5%). Average difference between the two calculation methods ranged between 0.6% and 36.3%, and this difference was strongly negatively correlated with water flux rate. Average water influx rates ranged between 15.5 g/day (fasting) and 624.5 g/day (feeding on cockles). The latter value is at 26.6 times the allometrically predicted value and is the highest reported to date. Differences in (2)H concentrations between the blood and feces (i.e., biological fractionation) were small but significant (-3.4% when fed a pellet diet, and -1.1% for all the other diets), and did not relate to the rate of water flux (chi(2)(1) = 0.058, P < 0.81). We conclude that the ingested water equilibrated rapidly with the body water pool even in an avian species that shows record water flux rates when living on ingested marine bivalves. 相似文献