Modeling Climate Change Effects on Streams and Reservoirs with HSPF

This study deals with the effects of the expected climate change on the hydrology of watersheds and on water resources. HSPF (Hydrological Simulation Program—Fortran) has been used to model streamflow and reservoir volume as realizations of watershed response. Climate change scenarios have been prepared based on trends expected in western Turkey in the first half of the twenty-first century and a hypothetical watershed with different land uses has been simulated. Changes in streamflow due to landuse, soil type and climate change have been examined using flood frequency and low flow analysis. The simulations have revealed quantitatively the difference among the responses of watersheds with no vegetative cover and with forests or pasture to trends in temperature and precipitation. It has also been found that monthly variations are very important in predicting the future response of watersheds. Significant differences have been observed in streamflows and reservoir volumes on a monthly basis between scenarios, soil types and land uses. Though the effects of temperature and precipitation act to counterbalance their effects on a long-term scale, on a monthly basis they can act to reinforce their effects and create drought periods and floods.     

Performance of a Monthly Streamflow Prediction Model for Ungauged Watersheds in Spain

Climate change, drought and the world??s growing population are increasing the demand for water which in turn requires improved water resources management. The sustainable management of a watershed requires a thorough knowledge of its water resources, including monthly streamflow. Spain is home to a large number of ungauged watersheds, the streamflows of which are often unknown. Chavez et al. (2007) reported a model for predicting monthly streamflow in ungauged watersheds that was validated for use in areas of tropical climate in Central America and a dry area in South America. This work reports an attempt to assess the performance of this model for eventual use with ungauged watersheds in Spain, using data for a number of watersheds for which gauging data were available. The proposed model took into account physical characteristics such us the soil infiltration rate, the slope of the terrain, plant fractional cover, the monthly moisture adequacy index, and the leaf area index. Comparisons of model-predicted monthly streamflows and those actually measured showed the Chavez et al. model unable to make reliable predictions for Spanish watersheds in its current form. A new approach has been developed considering only smaller watersheds in Spanish conditions, changing parameters in the original model. These parameters have been calibrated and validated, reaching adequate adjustment of results.     

海河流域径流变化趋势及其归因分析

在气候变化和人类活动共同影响下,流域径流发生了很大变化。尤其是海河流域,水资源匮乏的现象更为严重,分析水资源变化趋势对实现水资源的可持续开发利用具有重要意义。根据海河流域实际地形地貌特征及水文站分布情况,选取观台、响水堡、张家坟、下会和桃林口等5个水文站所在的区域,采用Mann-Kendall秩次相关检验法及线性回归方法,分析检验各典型区域年径流量的历史变化趋势。基于半分布式流域水文模型——TOPMODEL,采用水文模拟的途径,定量评估了典型区域气候变化和人类活动对径流变化的影响。归因结果表明:除桃林口外的其他4个水文站的年径流量均呈显著减小趋势,海河典型区域年径流减小主要跟人类活动有关,其占比都在65%以上。人类活动对观台、张家坟和响水堡站径流量减小的影响占比为65%~70%,对桃林口站径流量减小的影响占比为75.4%,对下会站径流量减小的影响占比高达81.7%,主要原因是海河流域自20世纪60年代中后期以来进行大规模水利建设所产生的水文效应。     

Dynamics of wet‐season turbidity in relation to precipitation,discharge, and land cover in three urbanizing watersheds,Oregon

Frequent intense precipitation events can mobilize and carry sediment and pollutants into rivers, degrading water quality. However, how seasonal rainfall and land cover affect the complex relationship between discharge and turbidity in urban watersheds is still under investigation. Using hourly discharge, rainfall, and turbidity data collected from six stations in three adjacent watersheds between 2008 and 2017, we examined the temporal variability of the discharge–turbidity relationship along an urban–rural gradient. We quantified hysteresis between normalized discharge and turbidity by a hysteresis index and classified hysteresis loops during 377 storm events in early, mid, and late wet season. Hysteresis loop index and direction varied by site land cover type and season. Turbidity values peaked quicker in the watersheds with higher degrees of urban development than in a less urbanized watershed. The positive relation between discharge and turbidity was highest in two downstream stations in the mid wet season, whereas it was highest in two upstream stations in the early wet season. Correlation and regression analysis showed that maximum turbidity was best explained by discharge range, and the sensitivity of turbidity to discharge change was higher in the larger downstream watershed than in the small upstream watersheds. A flashiness index was negatively associated with the slope of turbidity versus discharge, suggesting that turbidity is difficult to predict solely on the basis of discharge in flashy urban streams. This paper contributes to a deeper understanding of the spatial and temporal variation of discharge–concentration relationship in urbanizing watersheds, which can help water managers increase the resiliency of water‐related ecosystem services to impacts of climate change.     

Impact of Future Climate Change on Water Temperature and Thermal Habitat for Keystone Fishes in the Lower Saint John River,Canada

Water temperature is a key determinant of biological processes in rivers. Temperature in northern latitude rivers is expected to increase under climate change, with potentially adverse consequences for cold water-adapted species. In Canada, little is currently known about the timescales or magnitude of river temperature change, particularly in large (≥10⁴ km²) watersheds. However, because Canadian watersheds are home to a large number of temperature-sensitive organisms, there is a pressing need to understand the potential impacts of climate change on thermal habitats. This paper presents the results of a study to simulate the effects of climate change on the thermal regime of the lower Saint John River (SJR), a large, heavily impounded, socio-economically important watershed in eastern Canada. The CEQUEAU hydrological-water temperature model was calibrated against river temperature observations and driven using meteorological projections from a series of regional climate models. Changes in water temperature were assessed for three future periods (2030–2034, 2070–2074 and 2095–2099). Results show that mean water temperature in the SJR will increase by approximately ~1 °C by 2070–2074 and a further ~1 °C by 2095–2099, with similar findings for the maximum, minimum and standard deviation. We calculated a range of temperature metrics pertaining to the Atlantic Salmon and Striped Bass, key species within the SJR. Results show that while the SJR will become increasingly thermally-limiting for Atlantic Salmon, the Striped Bass growth season may actually lengthen under climate change. These results provide an insight into how climate change may affect thermal habitats for fish in eastern Canadian rivers.     

Optimal Ecological Management Practices (EMPs) for Minimizing the Impact of Climate Change and Watershed Degradation Due to Urbanization

Massive deforestation induced by unplanned urbanization in the hilly watersheds of Brahmaputra basin, India, has led to ecological imbalance and is gradually transforming this basin into a multi-hazard zone. Removal of green cover is also becoming a matter of global concern, as it can accelerate the adverse impacts of climate change. People coming in search of work generally reside in the hills, as they cannot afford the high cost of land in plains. This has led to deforestation of the hilly area and has resulted in increased surface erosion from the upper catchments. Though sediment and water yield from these degraded watersheds could have been minimized by implementing ecologically sustainable management practices (EMPs), such as grass land, forest land and detention pond, poor economic conditions of the people stands in the way of field implementation. On the other hand, major industries, which can be held responsible for emission of greenhouse gases, can be asked to finance greenery development in these hilly watersheds through implementation of selected EMPs to earn carbon credit for them. To convert this concept into reality, the EMP combination must be selected in such a way that it restricts sediment and water yield from the watershed within the permissible limit and maximizes its carbon sequestration capacity at minimum possible cost. Such optimal planning is a prerequisite for preparing an acceptable logical agreement between Government and private companies. Keeping this in mind, an optimization model was developed and applied to a micro watershed of Guwahati to explore its applicability in actual field. The model developed in this study provides most logical carbon credit negotiation, subject to the availability of reliable value of CO₂ sequestration for different EMPs.     

The Transferability of Terrestrial Water Balance Components under Uncertainty and Nonstationarity: A Case Study of the Coastal Plain Watershed in the Southeastern USA

The challenges posed by nonstationarity in predicting catchment water balance components motivated this study to test the stationary versus nonstationarity hypothesis and detect changes in the watershed response to land use land cover (LULC) alterations, and climate variability and change. The focus is on a two‐step procedure that includes model calibration of Soil and Water Assessment Tool using a sequential Bayesian uncertainty algorithm (i.e. sequential uncertainty fitting), followed by nonstationary assessment of water balance component using extreme value analysis over an Atlantic coastal plain watershed in the southeastern USA. Analysis suggests that the uncertainty of Soil and Water Assessment Tool model is statistically aligned with LULC alterations that increased the sensitivity of Manning's roughness coefficient, transmission loss and the resistance of the soil matrix to water flow. Changes in LULC along with variability in the magnitude, timing and frequency of precipitation diminished surface runoff and groundwater contribution to the river system whereas it increased evapotranspiration with a substantial decline in water storage capacity. Nonstationary assessment of water balance using extreme value analysis model further revealed a functional form of stationary behaviour (no trends) prior to LULC alteration while large amplification was detected during post‐changes. The results and findings presented in this paper confirm our hypothesis about a combined effect of climate and LULC changes on hydrological functions and that variation of these fingerprints elucidates the presence of nonstationarity in the watershed system. Copyright © 2017 John Wiley & Sons, Ltd.     

Development of a Demand Driven Hydro-climatic Model for Drought Planning

In recent years, droughts with increasing severity and frequency have been experienced around the world due to climate change effects. Water planning and management during droughts needs to deal with water demand variability, uncertainties in streamflow prediction, conflicts over water resources allocation, and the absence of necessary emergency schemes in drought situations. Reservoirs could play an important role in drought mitigation; therefore, development of an algorithm for operation of reservoirs in drought periods could help to mitigate the drought impacts by reducing the expected water shortages. For this purpose, the probable drought’s characteristics and their variations in response to factors such as climate change should be incorporated. This study aims at developing a contingency planning scheme for operation of reservoirs in drought periods using hedging rules with the objective of decreasing the maximum water deficit. The case study for evaluation of the performance of the proposed algorithm is the Sattarkhan reservoir in the Aharchay watershed, located in the northwestern part of Iran. The trend evaluations of the hydro-climatic variables show that the climate change has already affected streamflow in the region and has increased water scarcity and drought severity. To incorporate the climate change study in reservoir planning; streamflow should be simulated under climate change impacts. For this purpose, the climatic variables including temperature and precipitation in the future under climate change impacts are simulated using downscaled GCM (General Circulation Model) outputs to derive scenarios for possible future drought events. Then a hydrological model is developed to simulate the river streamflow, based on the downscaled data. The results show that the proposed methodology leads to less water deficit and decreases the drought damages in the study area.     

Modelling the Potential Impacts of Climate Change on Snowpack in the North Saskatchewan River Watershed, Alberta

The North Saskatchewan River basin is a large watershed in central Alberta that provides water for a range of stakeholders, including large municipalities, agricultural operations, power generation, and resource extraction industries. This study assesses potential future changes in snowpack for the North Saskatchewan River watershed in response to a range of GCM-derived climate warming scenarios representing the periods from 2010-2039 (2020s), 2040-2069 (2050s), and 2070-2099 (2080s). The GENESYS (GENerate Earth SYstems Science input) spatial hydrometeorological model is applied to simulate potential changes in the zero degree isotherm, precipitation phase, watershed average maximum spring snow water equivalent (SWE), the dates of maximum and minimum SWE, and snowmelt period for these future climate scenarios. Climate warming is likely to result in an upwards shift in elevation of the zero degree isotherm, with a transition to more precipitation occurring as rain than snow. Although watershed average maximum SWE may not change under future conditions, the timing of spring snowmelt onset is likely to change under the future climate scenarios applied. It is demonstrated that increased air temperatures are expected to result in substantial changes in snowpack processes in the North Saskatchewan River watershed.     

Landscape-scale modeling of water quality in Lake Superior and Lake Michigan watersheds: How useful are forest-based indicators?

The Great Lakes watersheds have an important influence on the water quality of the nearshore environment, therefore, watershed characteristics can be used to predict what will be observed in the streams. We used novel landscape information describing the forest cover change, along with forest census data and established land cover data to predict total phosphorus and turbidity in Great Lakes streams. In Lake Superior, we modeled increased phosphorus as a function of the increase in the proportion of persisting forest, forest disturbed during 2000–2009, and agricultural land, and we modeled increased turbidity as a function of the increase in the proportion of persisting forest, forest disturbed during 2000–2009, agricultural land, and urban land. In Lake Michigan, we modeled increased phosphorus as a function of ecoregion, decrease in the proportion of forest disturbed during 1984–1999 and watershed storage, and increase in the proportion of urban land, and we modeled increased turbidity as a function of ecoregion, increase in the proportion of forest disturbed during 2000–2009, and decrease in the proportion softwood forest. We used these relationships to identify priority areas for restoration in the Lake Superior basin in the southwestern watersheds, and in west central and southwest watersheds of the Lake Michigan basin. We then used the models to estimate water quality in watersheds without observed instream data to prioritize those areas for management. Prioritizing watersheds will aid effective management of the Great Lakes watershed and result in efficient use of restoration funds, which will lead to improved nearshore water quality.     

Interacting effects of climate change and agricultural BMPs on nutrient runoff entering Lake Erie

Agricultural best management practices (BMPs) have been implemented in the watersheds around Lake Erie to reduce nutrient transfer from terrestrial to aquatic ecosystems and thus protect and improve the water quality of Lake Erie. However, climate change may alter the effectiveness of these BMPs by altering runoff and other conditions. Using the Soil and Water Assessment Tool (SWAT), we simulated various climate scenarios with a range of BMPs to assess possible changes in water, sediment, and nutrient yields from four agricultural Lake Erie watersheds. Tile drain flow is expected to increase as is the amount of sediment that washes from land into streams. Predicted increases in tributary water flow (up to 17%), sediment yields (up to 32%), and nutrient yields (up to 23%) indicate a stronger influence of climate on sediment compared to other properties. Our simulations found much greater yield increases associated with scenarios of more pronounced climate change, indicating that above some threshold climate change may markedly accelerate sediment and nutrient export. Our results indicate that agricultural BMPs become more necessary but less effective under future climates; nonetheless, higher BMP implementation rates still could substantially offset anticipated increases in sediment and nutrient yields. Individual watersheds differ in their responsiveness to future climate scenarios, indicating the importance of targeting specific management strategies for individual watersheds.     

Robust Siting of Permeable Pavement in Highly Urbanized Watersheds Considering Climate Change Using a Combination of Fuzzy-TOPSIS and the VIKOR Method

Selecting an optimal location to maximize low impact development (LID) efficiency while accounting for future climate change is a difficult problem that requires multiple criteria to be considered. This study used a coupled approach of Fuzzy-TOPSIS and VIKOR to prioritize the best sites for permeable pavement in an urban watershed while considering climate change scenarios. The future climate change scenario known as shared socioeconomic pathways (SSPs) was used, with ten CMIP6 GCMs. Future monthly precipitation data were bias corrected using a quantile mapping method. The Mokgamcheon watershed, Korea, which has been highly urbanized, was selected, and its 27 sub-watersheds were determined to be the best candidate sites for permeable pavement. The evaluation criteria were determined based on the driving force-pressure-state-impact-response framework, and the corresponding values for the 27 sub-watersheds were obtained from national statistics, bias-corrected precipitation values, and simulations of the Storm Water Management Model (SWMM). The relative closeness to the positive ideal solution was calculated in each case using Fuzzy-TOPSIS, and priority scores were aggregated using the VIKOR method. The priority of permeable pavement was higher in the downstream watershed, which was more urbanized than in the upstream watershed. The results of this study can be helpful to establish a plan for improving the water cycles in urban watersheds under future climate change scenarios.

     

Climate change impact on water quality in the integrated Mahabad Dam watershed-reservoir system

Climate change, besides global warming, is expected to intensify the hydrological cycle, which can impact watershed nutrient yields and affect water quality in the receiving water bodies. The Mahabad Dam Reservoir in northwest Iran is a eutrophic reservoir due to excessive watershed nutrient input, which could be exacerbated due to climate change. In this regard, a holistic approach was employed by linking a climate model (CanESM2), watershed-scale model (SWAT), and reservoir water quality model (CE-QUAL-W2). The triple model investigates the cumulative climate change effects on hydrological parameters, watershed yields, and the reservoir’s water quality. The SDSM model downscaled the output of the climate model under moderate (RCP4.5) and extreme (RCP8.5) scenarios for the periods of 2021–2040 and 2041–2060. The impact of future climate conditions was investigated on the watershed runoff and total phosphorus (TP) load, and consequently, water quality status in the dam’s reservoir. The results of comparing future conditions (2021–2060) with observed present values under moderate to extreme climate scenarios showed a 4–7% temperature increase and a 6–11% precipitation decrease. Moreover, the SWAT model showed a 9–16% decline in streamflow and a 12–18% decline in the watershed TP load for the same comparative period. Finally, CE-QUAL-W2 model results showed a 3–8% increase in the reservoir water temperature and a 10–16% increase in TP concentration. It indicates that climate change would intensify the thermal stratification and eutrophication level in the reservoir, especially during the year’s warm months. This finding specifies an alarming condition that demands serious preventive and corrective measures.     

The Ven Te Chow Memorial Lecture: On Future Professional Activities Of The International Water Resources Association

ABSTRACT

The Upper Mississippi River Basin has experienced considerable hydrologic change in the last two centuries as a result of removal of wetland areas, deforestation and subsequent reforestation, changes in agricultural practices, urbanization, navigation projects, and the construction of levees. It is popularly accepted that the human-induced modifications to the river and its watersheds have increased the amount of flow in the Mississippi River, particularly during flooding events. Long-term streamgage records in the Upper Mississippi River Basin were analyzed to determine trends in streamflows and flooding. Over the 130 years of gaging there have been various periods in which the frequency and magnitude of floods have fluctuated. Trends in average flow and flooding are strongly correlated to coincident increases in average annual precipitation. For many portions of the watershed, precipitation and streamflows over the last three decades have been higher than any earlie period on record. Outside of the dominant influence of climate variation, only one major change on Mississippi River flood discharges is observed. Flood control reservoirs in the Missouri River watershed appear to produce a 10 per cent reduction in the average flood peak and average flood volume for the Mississippi River at St. Louis, Missouri.     

黄土高塬沟壑区水土保持对小流域地表径流的影响

水土保持对径流的作用是水土流失治理中一个亟待回答的实际问题．本文用小流域平行对比观测法，分析了黄土高塬沟壑区水土保持对小流域地表径流的数量及其时间分布特征的影响，表明在黄土高塬沟壑区，水土保持能使小流域产洪次数减少、地表径流模数和径流系数减小；使小流域地表径流模数的年际变率增大；在洪水产流过程中，水土保持使流域产流起始时间滞后，径流持续时间缩短，瞬时流量及洪峰流量降低以至消失     

Watershed Modeling to Assessing Impacts of Potential Climate Change on Water Supply Availability

Climate change could have impacts on hydrologic systems threatening, availability of water supply resources. In Illinois, regional water supply planning efforts are attempting to better understand potential impacts on low flow and surface water availability through analysis of hydrologic sensitivity to a range of climate scenarios. This paper explores the development, calibration and validation of Fox River watershed model using the soil and water assessment tool (SWAT) and the model’s application to assess impacts of potential climate change. The watershed model is calibrated and validated using daily flow records at three gauging stations. Automatic model calibration followed by manual refinement of parameter values was performed. Calibration results were generally good for monthly and annual time step but only satisfactory for daily simulations. Based on simulations of global climate models produced for IPCC fourth assessment report, climate scenarios were prepared by the Illinois State Water Survey for water supply planning initiatives in north-east and east-central Illinois. These scenarios showed ranges of temperature change between 0°C to +3.3°C and annual precipitation changes between −127 to +127 mm in the next 50 years, excluding the 5% extreme ends of those climate model simulations considered. Changes in climate were reflected using adjustments to the historical record, instead of using direct outputs from individual climate models. The watershed model was used to assess the impact of potential climate change. Application results indicate that annual precipitation change of 127 mm on average increases annual water yield and 7-day low flows by 28% and 19%, respectively. In contrast, a temperature change of +3.3°C results in average reductions of annual water yield by 13% and 7-day low flows by 10%. Seasonal effects were investigated through evaluation of changes in average monthly flows. Increasing precipitation resulted in significant changes in streamflows in late summer and fall months where as increasing temperature greatly affects winter flows due to snowmelt. The key implication is that climate change-induced variability of streamflows could have major impacts on water supply availability in the Fox River watershed and in particular, increased periods of drought could result in deficit of supplies during seasons of peak water use. It must be noted that this analysis does not examine the potential impacts of population growth and water use on water supply availability, which are also expected to have substantial influences in the region.     

Climate Change Impacts on Water Resources and Lake Regulation in the Vuoksi Watershed in Finland

The impacts of climate change on hydrology and water resources in the Vuoksi watershed in eastern Finland were studied in order to assess the possibilities to adapt lake regulation to the projected changes. A conceptual watershed model and several climate scenarios were used to estimate the effects of climate change on three lakes in the Vuoksi watershed for 2010–2039, 2040–2069 and 2070–2099. The adaptation possibilities were studied by using alternative regulation strategies. In Lake Pielinen the impacts of these water level changes on social, economic and ecological indicators were assessed with two different outflow strategies. According to the results, climate change will alter snow accumulation and melt and therefore cause large seasonal changes in runoff and water levels. Runoff and water levels will decrease during late spring and summer and increase during late autumn and winter. In some lakes current calendar-based regulation practices and limits, which have been developed based on past hydrology, may not be appropriate in the future. Modifying the regulation practices and limits is a necessary and effective way to adapt to climate change.     

Diagnosing Climate Change and Hydrological Responses in the Past Decades for a Minimally-disturbed Headwater Basin in South China

Identifying the trends of climate and hydrological changes is important for developing adaptive strategies for effective water resources management. Many studies focused on the prediction of future climate at a regional/global scale using General Circulation Models (GCM) or these models’ downscaled outcomes. However, diagnosing historical trends is regarded valuable for local areas, especially considering the spatial heterogeneity (both occurrence and magnitude) of climate change and uncertainty of climate projection. In this study, we selected the headwater area of the East River Basin in South China, which has minimal human-induced disturbance, to detect climate change and its hydrological changes over a past 50-year (1955–2004) time period. Although the climate warming agreed with the global situation, its magnitude was small and no sign of intensified rainfall or change of annual rainfall was found. Nevertheless, no-rain days increased and light-rain days decreased, indicating a longer dry interval between rainfall events. There was a significant downtrend of wind speed with a substantial reduction in magnitude, resulting in a decrease in the estimated potential evapotranspiration and a slight increase in the soil water content. Risks of flooding may not be a big concern, but water availability may be affected marginally in May and June due to the decreased rainfall and increased no-rain days. Overall, our results can improve the understanding of climate change and help watershed managers take precautions when facing climate change. This study also implies the necessity of investigating climate change at a local scale and at different time scales.     

Hydroclimatic variability across the international Lake of the Woods watershed: Implications for nutrient export and climate sensitivity

Characterizing streamflow and relationships with climate and watershed characteristics is an essential first step in the design of any monitoring program to assess basin response to changes in land use or climate. This is especially true for the international Lake of the Woods watershed, where recurrent algae blooms have been associated with nutrient inputs from the watershed and climate warming. Here, we present a basin-wide hydroclimatic analysis within the sparsely monitored Canadian portion of the basin. Spatial and temporal patterns in climate and runoff were assessed across the two major geo-zones: the Precambrian ‘Shield zone’, dominated by bedrock, forests and lakes, and the poorly drained ‘Agassiz zone’ where ditching and drainage for agriculture have substantially enhanced the hydrologic connectivity. While climate conditions were consistent across the watershed, Agassiz basins were flashy, highly variable, and more seasonal compared with Shield rivers, likely due to the moderating effect of lake storage in the Shield region. Temperatures increased across the basin (1910–2010), and there was more rainfall and runoff during the ice-covered months (Nov-Mar), suggesting a shift toward earlier snowmelt. Marked seasonality and large swings in flow extremes at the Agassiz rivers suggest this region is particularly sensitive to hydroclimatic change and that frequent monitoring is needed to capture important periods of nutrient export like spring runoff and storm events. In contrast, substantial storage within the Shield landscape suggests this zone is more hydrologically ‘resilient’ to climate extremes and that water quality and quantity measurements can be less frequent.     

基于水文模型与遥感信息的植被变化水文响应分析

针对地表覆被改变带来的流域水文响应存在不确定性这一问题,为了探索我国南方山区植被变化下的水文过程时空演变规律,依据东江流域的土地覆被类型,结合野外调查试验与遥感数据提取典型植被特征信息,利用考虑水文、地形、土壤、植被等多要素综合的分布式水文模型DHSVM,对流域内各种典型覆被情景下的水文过程进行模拟,进而分析植被变化引起的径流、蒸发、土壤水变化的响应关系。结果表明:大面积人工种植桉树林,将会对流域水文过程产生较大影响,地表径流深比现状针叶林增大17.5%,蒸散发量减小18.1%,洪峰流量也有所增加,流域洪水灾害发生概率加大;当流域现有针叶林生态系统退化为草地时,多年平均径流量增加24.4%,蒸散量减少25.3%,不利于自然流域的水源含蓄;针叶林、阔叶林和混交林三类森林植被更替对流域的水文过程影响相比其他植被类型要小。研究成果为分析流域变化环境下的水文过程时空演变规律及其生态环境效应提供参考,对我国南方山区水资源管理规划和生态环境保护具有实际意义。