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1.
The surface mass balance for Greenland and Antarctica has been calculated using model data from an AMIP-type experiment for the period 1979?C2001 using the ECHAM5 spectral transform model at different triangular truncations. There is a significant reduction in the calculated ablation for the highest model resolution, T319 with an equivalent grid distance of ca 40?km. As a consequence the T319 model has a positive surface mass balance for both ice sheets during the period. For Greenland, the models at lower resolution, T106 and T63, on the other hand, have a much stronger ablation leading to a negative surface mass balance. Calculations have also been undertaken for a climate change experiment using the IPCC scenario A1B, with a T213 resolution (corresponding to a grid distance of some 60?km) and comparing two 30-year periods from the end of the twentieth century and the end of the twenty-first century, respectively. For Greenland there is change of 495?km3/year, going from a positive to a negative surface mass balance corresponding to a sea level rise of 1.4?mm/year. For Antarctica there is an increase in the positive surface mass balance of 285?km3/year corresponding to a sea level fall by 0.8?mm/year. The surface mass balance changes of the two ice sheets lead to a sea level rise of 7?cm at the end of this century compared to end of the twentieth century. Other possible mass losses such as due to changes in the calving of icebergs are not considered. It appears that such changes must increase significantly, and several times more than the surface mass balance changes, if the ice sheets are to make a major contribution to sea level rise this century. The model calculations indicate large inter-annual variations in all relevant parameters making it impossible to identify robust trends from the examined periods at the end of the twentieth century. The calculated inter-annual variations are similar in magnitude to observations. The 30-year trend in SMB at the end of the twenty-first century is significant. The increase in precipitation on the ice sheets follows closely the Clausius-Clapeyron relation and is the main reason for the increase in the surface mass balance of Antarctica. On Greenland precipitation in the form of snow is gradually starting to decrease and cannot compensate for the increase in ablation. Another factor is the proportionally higher temperature increase on Greenland leading to a larger ablation. It follows that a modest increase in temperature will not be sufficient to compensate for the increase in accumulation, but this will change when temperature increases go beyond any critical limit. Calculations show that such a limit for Greenland might well be passed during this century. For Antarctica this will take much longer and probably well into following centuries.  相似文献   

2.
While ocean circulation is driven by the formation of deep water in the North Atlantic and the Circum-Antarctic, the role of southern-sourced deep water formation in climate change is poorly understood. Here we address the balance of northern- and southern-sourced waters in the South Atlantic through the last glacial period using neodymium isotope ratios of authigenic ferromanganese oxides in thirteen deep sea cores from throughout the South Atlantic. The data indicate that northern-sourced water did not reach the Southern Ocean during the late glacial, and was replaced by southern-derived intermediate and deep waters. The high-resolution neodymium isotope record (~ 300 yr sample spacing) from two spliced deep Cape Basin sites indicates that over the last glacial period northern-sourced water mass export to the Southern Ocean was stronger during the major Greenland millennial warming intervals (and Southern Hemisphere cool periods), and particularly during the major interstadials 8, 12, and 14. Northern-sourced water mass export was weaker during Greenland stadials and reached minima during Heinrich Events. The benthic foraminiferal carbon isotopes in the same Cape Basin core reflect a partial control by Southern Hemisphere climate changes and indicate that deep water formation and ventilation occurred in the Southern Ocean during major Greenland cooling intervals (stadials). Together, neodymium isotopes and benthic carbon isotopes provide new information about water mass sourcing and circulation in deep Southern Ocean waters during rapid glacial climate changes. Combining carbon and neodymium isotopes can be used to monitor the relative proportion of northern- and southern-sourced waters in the Cape Basin to gain insight into the processes which control the carbon isotopic composition of deep waters. In this study we show that deep water formation and circulation was more important than biological productivity and nutrient regeneration changes for controlling the carbon isotope chemistry of Antarctic Bottom Water during millennial-scale glacial climate cycles. This observation also lends support to the hypothesis that ocean circulation is linked to interhemispheric climate changes on short timescales, and that ventilation in the glacial ocean rapidly switched between the northern and Southern Hemisphere on millennial timescales.  相似文献   

3.
In Mediterranean regions, the marked climatic seasonality and uneven precipitation distribution complicate the application of isotope mass balances to obtain meaningful basin-wide annual average evaporation rates. In the present study, a mass balance approach carried out on the Tavignanu River watershed in Corsica (France), showed unrealistic evaporation rate estimates: 10% for 2017–2018 and 1% for 2018–2019. This suggests that not only does evaporation alter the seasonal isotopic composition in the river, but that there is complex variability of the dominant water reservoirs contributing to the streamflow. Therefore, we propose a modified mass balance approach, including monthly quantifications of different water sources contributing to the river discharge. This allows the discrimination of isotopic variation occurring by evaporation from that originating by mixing processes. By applying this modified approach, we estimated evaporation rates on the Tavignanu River watershed that were in good agreement with results obtained by hydrological modelling: 40% for 2017–2018 and 46% for 2018–2019, respectively. An uncertainty analysis showed that evaporation rates obtained with the modified isotopic approach are close to those obtained with the non-modified approach. Therefore, we recommend using this modified isotope mass balance approach to estimate evaporation rates in such regions as the Mediterranean with high seasonality in hydrological processes.  相似文献   

4.
One‐time or short‐term lake water isotopic surveys are often employed to evaluate regional lake water balance. However, it can be difficult to determine the optimal time‐window for sampling to obtain a representative long‐term perspective of lake water balance in settings influenced by seasonal variations in precipitation, evaporative loss, glacial/snow meltwater, and larger seasonal shifts in isotopic composition of precipitation. This is especially true for areas of the Tibetan Plateau that are influenced by the summer Indian monsoon. Although high‐frequency sampling is always preferred as the most rigorous approach to characterize the water budget of lakes or watersheds, this may be impractical in remote regions and over large spatial scales. To assess the potential sensitivity of isotope balance characterization to seasonal variability, we used a weekly lake water isotope data set acquired over a period of 3 years on the Tibetan Plateau to evaluate the potential inaccuracies that might have arisen from using isotopic data collected during narrower time‐windows. For this assessment, we use weekly isotopic data collected during the study and assume that these sampling events were stand‐alone one‐time surveys. We then demonstrate the sensitivity of the isotope balance method in this setting, particularly for the rainy season that significantly underestimated the evaporation/inflow. In contrast, isotopic composition of the lake water was found to be more representative of long‐term conditions when sampled in October on the Tibetan Plateau. To broaden our evaluation of seasonality effects over a range of climatic zones, published high‐frequency isotopic data were also compiled, and a similar assessment was carried out for selected regions of the world. The synthesized data and model outputs, which confirm pronounced variations in lake water isotopic composition and evaporation/inflow across a range of seasonal climates, were used to determine optimal sampling windows for these specific regions.  相似文献   

5.
Climatologists have been paying much attention to the global and regional climatic charac-teristics during the LGM. A lot of paleodata were obtained in East Asia during the LGM[1—5] and laid the firm foundation of reconstructing East Asian paleoclimate t…  相似文献   

6.
中国末次冰盛期以来湖泊水量变化及古气候变化机制解释   总被引：2，自引：0，他引：2  
薛滨  于革 《湖泊科学》2005,17(1):35-40
中国古湖泊数据库收录的42个湖泊,提供的湖泊水量每千年变化的空间信息,可以用来系统分析中国区域末次冰盛期以来大气环流变化的状况.研究结果表明:我国西部从末次冰盛期以来直至全新世中期均为较湿润的气候状况,推测冰期内的湿润条件主要与西风带的降水以及低温低蒸发密切相关,而全新世主要为夏季风降水增加所致;全新世晚期气候趋干明显.我国东部的大部分区域在冰盛期和晚冰期较为干旱;只是在全新世有效降水状况才有大幅度的改善,全新世中期夏季风降水的效应仍然相当显著,控制的范围可达整个中国西部,同时位于现代季风气候区的中国东部,有效降水的峰值区的变化似乎存在从北往南的穿时性,南方有效降水峰值出现在晚全新世.而西南季风区湿润状况的明显改善发生在晚冰期,比东南季风区发生的早,显然这与两个季风系统的相互消长有一定的关系.我国东北区的湿润状况改善的也较早,显示了独特的季风气候机制.  相似文献   

7.
Stable water isotope ratios are measured as a tracer of environmental processes in materials such as leaves, soils, and lakes. Water in these archives may experience evaporation, which increases the abundance of heavy isotopologues proportionally to the gradients in humidity and isotope ratio between the evaporating water and the surrounding atmosphere. The isotope ratio of the atmosphere has been difficult to measure until recently, and measurements remain scarce. As a result, several assumptions have been adopted to estimate isotope ratios of atmospheric water vapour. Perhaps the most commonly employed assumption in terrestrial environments is that water vapour is in isotopic equilibrium with precipitation. We evaluate this assumption using an eight‐member ensemble of general circulation model (GCM) simulations that include explicit calculation of isotope ratios in precipitation and vapour. We find that across the model ensemble, water vapour is typically less depleted in heavy isotopologues than expected if it were in equilibrium with annual precipitation. Atmospheric vapour likely possesses higher‐than‐expected isotope ratios because precipitation isotope ratios are determined by atmospheric conditions that favour condensation, which do not reflect atmospheric mixing and advection processes outside of precipitation events. The effect of this deviation on theoretical estimates of isotope ratios of evaporating waters scales with relative humidity. As a result, the equilibrium assumption gives relatively accurate estimates of the isotope ratios of evaporating waters in low latitudes but performs increasingly poorly at increasing latitudes. Future studies of evaporative water pools should include measurements of atmospheric isotope ratios or constrain potential bias with isotope‐enabled GCM simulations.  相似文献   

8.
Groundwater, an essential resource, is likely to change with global warming because of changes in the CO2 levels, temperature and precipitation. Here, we combine water isotope geochemistry with climate modelling to examine future groundwater recharge in southwest Ohio, USA. We first establish the stable isotope profiles of oxygen and deuterium in precipitation and groundwater. We then use an isotope mass balance model to determine seasonal groundwater recharge from precipitation. Climate model output is used to project future changes in precipitation and its seasonal distribution under medium and high climate change scenarios. Finally, these results are combined to examine future changes in groundwater recharge. We find that 76% of the groundwater recharge occurs in the cool season. Climate models project precipitation increase in the cool season and decrease in the warm season. The total groundwater recharge is expected to increase by 3.2% (8.8%) under the medium (high) climate change scenarios.  相似文献   

9.
For given climatic rates of precipitation and potential evaporation, the land surface hydrology parameterizations of atmospheric general circulation models will maintain soil-water storage conditions that balance the moisture input and output. The surface relative soil saturation for such climatic conditions serves as a measure of the land surface parameterization state under a given forcing. The equilibrium value of this variable for alternate parameterizations of land surface hydrology are determined as a function of climate and the sensitivity of the surface to shifts and changes in climatic forcing are estimated.  相似文献   

10.
In mountainous river basins of the Pacific Northwest, climate models predict that winter warming will result in increased precipitation falling as rain and decreased snowpack. A detailed understanding of the spatial and temporal dynamics of water sources across river networks will help illuminate climate change impacts on river flow regimes. Because the stable isotopic composition of precipitation varies geographically, variation in surface water isotope ratios indicates the volume-weighted integration of upstream source water. We measured the stable isotope ratios of surface water samples collected in the Snoqualmie River basin in western Washington over June and September 2017 and the 2018 water year. We used ordinary least squares regression and geostatistical Spatial Stream Network models to relate surface water isotope ratios to mean watershed elevation (MWE) across seasons. Geologic and discharge data was integrated with water isotopes to create a conceptual model of streamflow generation for the Snoqualmie River. We found that surface water stable isotope ratios were lowest in the spring and highest in the dry, Mediterranean summer, but related strongly to MWE throughout the year. Low isotope ratios in spring reflect the input of snowmelt into high elevation tributaries. High summer isotope ratios suggest that groundwater is sourced from low elevation areas and recharged by winter precipitation. Overall, our results suggest that baseflow in the Snoqualmie River may be relatively resilient to predicted warming and subsequent changes to snowpack in the Pacific Northwest.  相似文献   

11.
The Chirripó hydrological research site (CHRS) is located within the Chirripó National Park, Costa Rica (between 3100 and 3820 m asl) whereby ~100 km2 are covered by Páramo, a high-elevation tropical grassland ecosystem. A lake district with approximately 30 lakes of glacial origin is also protected in this area. The CHRS has been monitored since April 2015 with the aim of establishing the first water isotope baseline for the Central American Páramo. At a regional scale, the water isotope ratios (δ2H and δ18O) in precipitation and surface water at CHRS are useful for describing the governing moisture transport from the Caribbean Sea and Pacific Ocean and the complex rainfall producing systems across the N–S mountain range of Central America. These data are also providing unique information about the evaporation and water balance conditions of tropical glacial lakes and the formation of orographic and convective precipitation in high-elevation tropical ecosystems. Current data sets from CHRS include continuous lake water temperature and meteorological conditions (i.e., precipitation amount, air temperature and relative humidity), as well as water stable isotopes in precipitation, stream water, and lake water (daily to biweekly sampling frequency). Stream water is collected at several locations across the topographic gradient whereas lake water is sampled in the three main lake systems of CHRS. CHRS serves as a reference site for conducting pilot isotopic research in high-elevation ecosystems to advance the atmospheric, hydrogeological and ecohydrological studies in these understudied biomes. All data from April 2015 to November 2020 are publicly available.  相似文献   

12.
Li  Yu  Zhang  Yuxin  Zhang  Xinzhong  Ye  Wangting  Xu  Lingmei  Han  Qin  Li  Yichan  Liu  Hebin  Peng  Simin 《中国科学:地球科学(英文版)》2020,63(8):1161-1175
The fluctuation of a single lake level is a comprehensive reflection of water balance within the basin, while the regional consistent fluctuations of lake level can indicate the change of regional effective moisture. Previous researches were mainly focused on reconstructing effective moisture by multiproxy analyses of lake sediments. We carried out a series of experiments, including a transient climate evolution model, a lake energy balance model and a lake water balance model to simulate continuous Holocene effective moisture change represented by variability of virtual lake level in East and Central Asia.The virtual lake level, area, water depth and salinity are not equivalent to actual values, but we estimated relative changes of the regional effective moisture. We also explored the driving mechanisms of effective moisture change in different geographical regions. Our results indicated that gradually falling effective moisture during the Holocene in northern China was due to the combined effects of high lake evaporation caused by longwave and shortwave radiation, and low precipitation caused by reductions of summer solar insolation. A decline in effective moisture through the Holocene in the Tibetan Plateau and southern Central Asia resulted from decreased precipitation because of the weakening of the Asian summer monsoon. Increased precipitation induced by the strengthening of the westerly circulation contributed to the effective moisture rise during the Holocene in northern Central Asia.  相似文献   

13.
R. K. SAXENA 《水文研究》1996,10(10):1273-1281
Lake evaporation has been estimated for a shallow lake using a combination of water and isotope mass balance, accounting for the isotopic non-steady state of lake water. The main feature of the isotope method is that inflows need not be measured. Knowledge of their isotopic content is sufficient. Oxygen-18 content, i.e. (δ18O), of lake water, inflows and outflow was measured on a weekly basis, whereas for precipitation it was monitored daily. The discharge from the lake was also recorded daily. Lake water level, relative humidity, air, and lake water surface temperatures were recorded by a logger. The weather data were recorded on a small island in the lake. It was observed that the lake is isotopically well mixed. Furthermore, the atmospheric moisture was not always in isotopic equilibrium with the precipitation. Daily lake evaporation was estimated as an average of six to eight days depending upon the field logistics. Lake evaporation varied from 0.6 to about 5.4 mm/day during the experimental period. It was found that evaporation estimates are very sensitive to small variations in δ18O of lake evaporate. Induced changes of 10% in δ18O of lake evaporate caused errors in evaporation estimates of 9–31%, while similar induced changes in δ18O of inflows caused errors of 8–18%. Thus, an accurate experimental determination of δ18O of lake evaporate is relatively more important.  相似文献   

14.
Numerous socio-economic activities depend on the seasonal rainfall and groundwater recharge cycle across the Central American Isthmus. Population growth and unregulated land use changes resulted in extensive surface water pollution and a large dependency on groundwater resources. This work combines stable isotope variations in rainfall, surface water, and groundwater of Costa Rica, Nicaragua, El Salvador, and Honduras to develop a regionalized rainfall isoscape, isotopic lapse rates, spatial–temporal isotopic variations, and air mass back trajectories determining potential mean recharge elevations, moisture circulation patterns, and surface water–groundwater interactions. Intra-seasonal rainfall modes resulted in two isotopically depleted incursions (W-shaped isotopic pattern) during the wet season and two enriched pulses during the mid-summer drought and the months of the strongest trade winds. Notable isotopic sub-cloud fractionation and near-surface secondary evaporation were identified as common denominators within the Central American Dry Corridor. Groundwater and surface water isotope ratios depicted the strong orographic separation into the Caribbean and Pacific domains, mainly induced by the governing moisture transport from the Caribbean Sea, complex rainfall producing systems across the N-S mountain range, and the subsequent mixing with local evapotranspiration, and, to a lesser degree, the eastern Pacific Ocean fluxes. Groundwater recharge was characterized by (a) depleted recharge in highland areas (72.3%), (b) rapid recharge via preferential flow paths (13.1%), and enriched recharge due to near-surface secondary fractionation (14.6%). Median recharge elevation ranged from 1,104 to 1,979 m a.s.l. These results are intended to enhance forest conservation practices, inform water protection regulations, and facilitate water security and sustainability planning in the Central American Isthmus.  相似文献   

15.
Summary The mean zonal and meridional wind components of the northern hemisphere at different pressure levels for the summer season June–August have been determined and the mean meridional mass circulation has been computed as a function of latitude. From the mass circulation the meridional flux of moisture is computed for the latitudinal belt 0°–45° N. Using the horizontal divergence of this flux the average difference between precipitation and evapotranspiration from the earth's surface is evaluated.  相似文献   

16.
Western disturbances (WDs) and Indian summer monsoon (ISM) led precipitation play a central role in the Himalayan water budget. Estimating their contributions to water resource is although a challenging but essential for hydrologic understanding and effective water resource management. In this study, we used stable water isotope data of precipitation and surface waters to estimate the contribution of ISM and WDs to the water resources in three mountainous river basins - Indus, Bhagirathi and Teesta river basins of western, central and Eastern Himalayas. The study reveals distinct seasonality in isotope characteristics of precipitation and surface waters in each river basin is due to changes in moisture source, hydrometeorology and relief. Despite steady spatial variance in the slope and intercept of regression lines from the Teesta to Indus and the Bhagirathi river basins, the slope and intercept are close to the global meteoric water line and reported local meteoric water line of other regions in the Himalayas and the Tibetan Plateau. The two-component end-member mixing method using d-excess as tracer were used to estimate the contribution from ISM and WD led precipitation to surface water in aforementioned river basins. The results suggest that the influence of the ISM on the water resources is high (>72% to annual river flow) in Teesta river basin (eastern Himalayas), while as the WDs led precipitation is dominantly contributing (>70% average annual river flow) to the surface waters in the Indus river basin (western Himalayas). The contribution of ISM and WD led precipitation in Bhagirathi river basin is 60% and 40%, respectively. The findings demonstrate that the unusual changes in the ISM and WD moisture dynamics have the potential to affect the economy and food security of the region, which is dependent on the availability of water resources. The obtained results are of assistance to policy makers/mangers to make use of the information for better understanding hydrologic response amid unusual behaviour of the dual monsoon system over the region.  相似文献   

17.
The time mean response of the summer monsoon circulation, as simulated by the 2.5° latitude-longitude resolution, July version of the National Center for Atmospheric Research (NCAR) General Circulation Model (GCM), to a variety of Indian Ocean surface temperature anomaly patterns is examined. In separate experiments, prescribed changes in surface temperature are imposed in the Western Arabian Sea, the Eastern Arbian Sea or the Central Indian Ocean. The influence of these anomaly patterns on the simulated summer monsoon circulation is evaluated in terms of the geographical distribution of the prescribed change response for any field of interest. This response is defined as the grid point difference between a 30-day mean from a prescribed change experiment and the ensemble average of the 30-day means from the control population for which the same set of climatological ocean surface temperatures are used in each simulation. The statistical significance of such a prescribed change response is estimated by relating the normalized response (defined as the ratio of the prescribed change response to the standard deviation of 30-day means as estimated from the finite sample of control cases) to the classical Student'st-statistic. Using this methodology, the most prominent and statistically significant features of the model's response are increased vertical velocity and precipitation over warm anomalies and typically decreased vertical velocity and precipitation in some preferred region adjacent to the prescribed change region. In the case of cold anomalies, these changes are of opposite sign. However, none of the imposed anomaly patterns produces substantial or statistically significant precipitation changes over large areas of the Indian sub-continent. The only evidence of a major nonlocal effect is found in the experiment with a large positive anomaly (+3°C) in the Central Indian Ocean. In this instance, vertical velocity and precipitation are reduced over Malaysia and a large area of the Equatorial Western Pacific Ocean. Thus, while these anomaly experiments produce only a local response (for the most part), it is hoped, as one of the purposes of the planned Monsoon Experiment (MONEX), that the necessary data will be provided to produce detailed empirical evidence on the extent to which Indian Ocean surface temperature anomalies correlate with precipitation anomalies over the Indian subcontinent—a correlation which generally does not appear in these GCM results.The National Center for Atmospheric Research is sponsored by the National Science Foundation  相似文献   

18.
We have used satellite solutions to the low degree zonal harmonics of the Earth's gravitational potential, and rates of surface accumulation to partially constrain, by means of repeated forward solution, the time rates of thickness change over the Antarctic and Greenland Ice Sheets (dTA and dTG respectively). In addition to the observed zonal coefficients j2 through j5 we impose only one other constraint: That dTA and dTG are proportional to surface accumulation. The lagged response of the Earth to secular changes in ice thickness spanning recent time periods (up to 2000 years before present) and the late Pleistocene is accounted for by means of two viscoelastic rebound models. The sea level contributions from the ice sheets, calculated from dTA and dTG, lower mantle viscosity, and the start time of present-day thickness change are all variables subject to the constraints. For a given set of post glacial rebound inputs, a family of solutions that have similar characteristics and that agree well with observation are obtained from the large number of forward solutions. The off axis position of the Greenland ice sheet makes its contribution to the low degree zonal coefficients less sensitive to the spatial details of the mass balance than to the overall sea level contribution. dTG is therefore modeled as surface mass balance offset by a uniform and constant mass loss. Though dTA varies widely with choices of input parameters, the combined sea level contribution from both ice sheets is reasonably well constrained by the gravity coefficients, and is predicted to range from -0.9 to +1.6 mm yr-1. The sign of the slope of the low degree zonal coefficients versus sea level contribution for Greenland is positive, but for Antarctica, the sign of the slope is positive for even degree and negative for odd degree harmonics. By using this property of the zonal coefficients, it is possible to determine the individual sea level contributions for Greenland and Antarctica. They vary from -0.6 to +0.3 mm yr-1 for the Greenland Ice Sheet, and from -0.3 to +1.3 mm yr-1 for the Antarctic Ice Sheet.  相似文献   

19.
During the Late Cretaceous, western North America was characterized by a close geographic association between the Sevier highlands and the Western Interior Seaway. In this paper, an atmospheric general circulation model (AGCM) is used to simulate the impact of this geographic association on surface pressure, wind direction, and precipitation, and it is predicted that seasonal changes in these variables resulted in a strong monsoon along the eastern flank of the Sevier Highlands. Confirmation that these model simulations are accurate is provided by isotopic data from foreland basin sediments. In particular oxygen isotope records from different environments (large rivers, small streams and ponds) and proxies (unionid bivalve shells and paleosol carbonates) indicate that foreland basin streams were recharged by local precipitation with high oxygen isotope ratios while large trunk rivers were recharged by high-elevation precipitation. This hydrologic pattern is observed from Alberta to Utah and is consistent with east to west monsoonal air mass movements and associated seasonal rainfall. Recognition of a highland-driven monsoon has implication in regard to studies of fossil taphonomy, of water vapor transport, and of links between climate and mountain uplift and exhumation in this region.  相似文献   

20.
Quantification of water balance components, under arid conditions, is essential to the development of water management policies. This study demonstrates the application of the mass water balance approach for the assessment of water resources in a typical watershed located in the southwestern region of Saudi Arabia. The water balance approach was used, on an event basis, to express the amount of precipitation for 13 storms over a three year period, as a percentage of other hydrological components such as runoff, evaporation, and recharge. The study indicated that 63 per cent of precipitation is lost through evaporation from the water surface during flooding, and from the upper layers of the soil surface immediately after storms. Another 32 per cent is stored in the form of soil moisture in the unsaturated layers below the effective evaporation depth. Only 3 per cent of the precipitation was transformed into surface runoff; however, 75 per cent of this contributes towards groundwater recharge. This study has illustrated that the mass water balance approach can be used, with reasonable accuracy, to quantify the components of the hydrological processes under arid conditions, where a reliable data base is available. This, in turn, will help in the development of appropriate water management policies for arid regions.  相似文献   

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