Improving monthly streamflow prediction in alpine regions: integrating HBV model with Bayesian neural network

Statistical methods have been widely used to build different streamflow prediction models; however, lacking of physical mechanism prevents precise streamflow prediction in alpine regions dominated by rainfall, snow and glacier. To improve precision, a new hybrid model (HBNN) integrating HBV hydrological model, Bayesian neural network (BNN) and uncertainty analysis is proposed. In this approach, the HBV is mainly used to generate initial snow-melt and glacier-melt runoffs that are regarded as new inputs of BNN for precision improvement. To examine model reliability, a hybrid deterministic model called HLSSVM incorporating the HBV model and least-square support vector machine is also developed and compared with HBNN in a typical region, the Yarkant River basin in Central Asia. The findings suggest that the HBNN model is a robust streamflow prediction model for alpine regions and capable of combining strengths of both the BNN statistical model and the HBV hydrological model, providing not only more precise streamflow prediction but also more reasonable uncertainty intervals than competitors particularly at high flows. It can be used in predicting streamflow for similar regions worldwide.     

人工神经网络模型预测气候变化对博斯腾湖流域径流影响

温室气体排放量增加造成气候变化,对全球资源环境产生重要影响．本文利用人工神经网络模型建立月降水、气温与径流关系,利用开都河流域降水、气温、径流资料对模型进行训练和验证,通过试算法确定网络模型结构,气温升高和降水量增加对径流影响的敏感程度分析表明,气温升高和降水增加对该区域径流影响较大,且气温升高的影响更为显著,径流增加主要集中在夏季,根据区域气候模型（RCMs）推算的CO2加倍情况下西北地区气候的可能变化,预测位于博斯腾湖流域的开都河大山口站年径流量增加38．6％,其中夏季增加71．8％,冬季增加11．4％。     

Vulnerability indicators of sea water intrusion

In this paper, simple indicators of the propensity for sea water intrusion (SWI) to occur (referred to as "SWI vulnerability indicators") are devised. The analysis is based on an existing analytical solution for the steady-state position of a sharp fresh water-salt water interface. Interface characteristics, that is, the wedge toe location and sea water volume, are used in quantifying SWI in both confined and unconfined aquifers. Rates-of-change (partial derivatives of the analytical solution) in the wedge toe or sea water volume are used to quantify the aquifer vulnerability to various stress situations, including (1) sea-level rise; (2) change in recharge (e.g., due to climate change); and (3) change in seaward discharge. A selection of coastal aquifer cases is used to apply the SWI vulnerability indicators, and the proposed methodology produces interpretations of SWI vulnerability that are broadly consistent with more comprehensive investigations. Several inferences regarding SWI vulnerability arise from the analysis, including: (1) sea-level rise impacts are more extensive in aquifers with head-controlled rather than flux-controlled inland boundaries, whereas the opposite is true for recharge change impacts; (2) sea-level rise does not induce SWI in constant-discharge confined aquifers; (3) SWI vulnerability varies depending on the causal factor, and therefore vulnerability composites are needed that differentiate vulnerability to such threats as sea-level rise, climate change, and changes in seaward groundwater discharge. We contend that the approach is an improvement over existing methods for characterizing SWI vulnerability, because the method has theoretical underpinnings and yet calculations are simple, although the coastal aquifer conceptualization is highly idealized.     

What dominates sea level at the coast: a case study for the Gulf of Guinea

Sea level variations and extreme events are a major threat for coastal zones. This threat is expected to worsen with time because low-lying coastal areas are expected to become more vulnerable to flooding and land loss as sea level rises in response to climate change. Sea level variations in the coastal ocean result from a combination of different processes that act at different spatial and temporal scales. In this study, the relative importance of processes causing coastal sea level variability at different time-scales is evaluated. Contributions from the altimetry-derived sea-level (including the sea level rise due to the ocean warming and land ice loss in response to climate change), dynamical atmospheric forcing induced sea level (surges), wave-induced run-up and set-up, and astronomical tides are estimated from observational datasets and reanalyses. As these processes impact the coast differently, evaluating their importance is essential for assessment of the local coastline vulnerability. A case study is developed in the Gulf of Guinea over the 1993–2012 period. The leading contributors to sea level variability off Cotonou differ depending on the time-scales considered. The trend is largely dominated by processes included in altimetric data and to a lesser extent by swell-waves run-up. The latter dominates interannual variations. Swell-waves run-up and tides dominate subannual variability. Extreme events are due to the conjunction of high tides and large swell run-up, exhibiting a clear seasonal cycle with more events in boreal summer and a trend mostly related to the trend in altimetric-derived sea-level.     

Influences of climate,terrain and land cover on stream salinity in southeastern Australia,and implications for management through reforestation

Reforestation of cleared land has the potential to reduce groundwater recharge, salt mobilization and streamflow. Stream salinity change is the net result of changes in stream salt load and streamflow. The net effect of these changes varies spatially as a function of climate, terrain and land cover. Successful natural resource management requires methods to map the spatial variability of reforestation impacts. We investigated salinity data from 2000 bores and streamflow and salinity measurements from 27 catchments in the Goulburn–Broken region in southeast Australia to assess the main factors determining stream salinity and opportunities for management through reforestation. For groundwater systems of similar geology, relationships were found between average annual rainfall and groundwater salinity and between groundwater salinity and low‐flow salinity. Despite its simplicity, we found that the steady‐state component of a simple conceptual coupled water–salt mass balance model (BC2C) adequately explained the spatial variation in streamflow and salinity. The model results suggest the efficiency of afforestation to reduce stream salinity could be increased by more than an order of magnitude through spatial planning. However, appreciable reductions in stream salinity in large rivers through land cover change alone would still require reforestation on an unprecedented scale. Copyright © 2008 John Wiley & Sons, Ltd.     

Sea water intrusion by sea-level rise: scenarios for the 21st century

This study presents a method to assess the contributions of 21st-century sea-level rise and groundwater extraction to sea water intrusion in coastal aquifers. Sea water intrusion is represented by the landward advance of the 10,000 mg/L iso-salinity line, a concentration of dissolved salts that renders groundwater unsuitable for human use. A mathematical formulation of the resolution of sea water intrusion among its causes was quantified via numerical simulation under scenarios of change in groundwater extraction and sea-level rise in the 21st century. The developed method is illustrated with simulations of sea water intrusion in the Seaside Area sub-basin near the City of Monterey, California (USA), where predictions of mean sea-level rise through the early 21st century range from 0.10 to 0.90 m due to increasing global mean surface temperature. The modeling simulation was carried out with a state-of-the-art numerical model that accounts for the effects of salinity on groundwater density and can approximate hydrostratigraphic geometry closely. Simulations of sea water intrusion corresponding to various combinations of groundwater extraction and sea-level rise established that groundwater extraction is the predominant driver of sea water intrusion in the study aquifer. The method presented in this work is applicable to coastal aquifers under a variety of other scenarios of change not considered in this work. For example, one could resolve what changes in groundwater extraction and/or sea level would cause specified levels of groundwater salinization at strategic locations and times.     

Simulation and Analysis of Conjunctive Use with MODFLOW's Farm Process

The extension of MODFLOW onto the landscape with the Farm Process (MF-FMP) facilitates fully coupled simulation of the use and movement of water from precipitation, streamflow and runoff, groundwater flow, and consumption by natural and agricultural vegetation throughout the hydrologic system at all times. This allows for more complete analysis of conjunctive use water-resource systems than previously possible with MODFLOW by combining relevant aspects of the landscape with the groundwater and surface water components. This analysis is accomplished using distributed cell-by-cell supply-constrained and demand-driven components across the landscape within “water-balance subregions” comprised of one or more model cells that can represent a single farm, a group of farms, or other hydrologic or geopolitical entities. Simulation of micro-agriculture in the Pajaro Valley and macro-agriculture in the Central Valley are used to demonstrate the utility of MF-FMP. For Pajaro Valley, the simulation of an aquifer storage and recovery system and related coastal water distribution system to supplant coastal pumpage was analyzed subject to climate variations and additional supplemental sources such as local runoff. For the Central Valley, analysis of conjunctive use from different hydrologic settings of northern and southern subregions shows how and when precipitation, surface water, and groundwater are important to conjunctive use. The examples show that through MF-FMP's ability to simulate natural and anthropogenic components of the hydrologic cycle, the distribution and dynamics of supply and demand can be analyzed, understood, and managed. This analysis of conjunctive use would be difficult without embedding them in the simulation and are difficult to estimate a priori.     

River water quality response under hypothetical climate change scenarios in Tunga‐Bhadra river,India

Analysis of climate change impacts on streamflow by perturbing the climate inputs has been a concern for many authors in the past few years, but there are few analyses for the impacts on water quality. To examine the impact of change in climate variables on the water quality parameters, the water quality input variables have to be perturbed. The primary input variables that can be considered for such an analysis are streamflow and water temperature, which are affected by changes in precipitation and air temperature, respectively. Using hypothetical scenarios to represent both greenhouse warming and streamflow changes, the sensitivity of the water quality parameters has been evaluated under conditions of altered river flow and river temperature in this article. Historical data analysis of hydroclimatic variables is carried out, which includes flow duration exceedance percentage (e.g. Q90), single low‐flow indices (e.g. 7Q10, 30Q10) and relationships between climatic variables and surface variables. For the study region of Tunga‐Bhadra river in India, low flows are found to be decreasing and water temperatures are found to be increasing. As a result, there is a reduction in dissolved oxygen (DO) levels found in recent years. Water quality responses of six hypothetical climate change scenarios were simulated by the water quality model, QUAL2K. A simple linear regression relation between air and water temperature is used to generate the scenarios for river water temperature. The results suggest that all the hypothetical climate change scenarios would cause impairment in water quality. It was found that there is a significant decrease in DO levels due to the impact of climate change on temperature and flows, even when the discharges were at safe permissible levels set by pollution control agencies (PCAs). The necessity to improve the standards of PCA and develop adaptation policies for the dischargers to account for climate change is examined through a fuzzy waste load allocation model developed earlier. Copyright © 2011 John Wiley & Sons, Ltd.     

A spatially distributed model for the assessment of land use impacts on stream temperature in small urban watersheds

Stream temperatures in urban watersheds are influenced to a high degree by changes in landscape and climate, which can occur at small temporal and spatial scales. Here, we describe a modelling system that integrates the distributed hydrologic soil vegetation model with the semi‐Lagrangian stream temperature model RBM. It has the capability to simulate spatially distributed hydrology and water temperature over the entire network at high time and space resolutions, as well as to represent riparian shading effects on stream temperatures. We demonstrate the modelling system through application to the Mercer Creek watershed, a small urban catchment near Bellevue, Washington. The results suggest that the model was able to produce realistic streamflow and water temperature predictions that are consistent with observations. We use the modelling construct to characterize impacts of land use change and near‐stream vegetation change on stream temperatures and explore the sensitivity of stream temperature to changes in land use and riparian vegetation. The results suggest that, notwithstanding general warming as a result of climate change over the last century, there have been concurrent increases in low flows as a result of urbanization and deforestation, which more or less offset the effects of a warmer climate on stream temperatures. On the other hand, loss of riparian vegetation plays a more important role in modulating water temperatures, in particular, on annual maximum temperature (around 4 °C), which could be mostly reversed by restoring riparian vegetation in a fairly narrow corridor – a finding that has important implications for management of the riparian corridor. Copyright © 2014 John Wiley & Sons, Ltd.     

Nonlinear bacterial load‐streamflow response on a marine beach

Bacterial concentration (Escherichia coli) is used as the key indicator for marine beach water quality in Hong Kong. For beaches receiving streamflow from unsewered catchments, water quality is mainly affected by local nonpoint source pollution and is highly dependent on the bacterial load contributed from the catchment. As most of these catchments are ungauged, the bacterial load is generally unknown. In this study, streamflow and the associated bacterial load contributed from an unsewered catchment to a marine beach, Big Wave Bay, are simulated using a modelling approach. The physically based distributed hydrological model, MIKE‐SHE, and the empirical watershed water quality model (Hydrological Simulation Program – Fortran) are used to simulate streamflow and daily‐averaged E. coli concentration/load, respectively. The total daily derived loads predicted by the model during calibration (June–July 2007) and validation (July–October 2008) periods agree well with empirical validation data, with a percentage difference of 3 and 2%, respectively. The simulation results show a nonlinear relationship between E. coli load and rainfall/streamflow and reveal a source limiting nature of nonpoint source pollution. The derived load is further used as an independent variable in a multiple linear regression (MLR) model to predict daily beach water quality. When compared with the MLR models based solely on hydrometeorological input variables (e.g. rainfall and salinity), the new model based on bacterial load predicts much more realistic E. coli concentrations during rainstorms. Copyright © 2014 John Wiley & Sons, Ltd.     

Integrated Hydrological Modeling of Climate Change Impacts in a Snow-Influenced Catchment

The potential impact of climate change on water resources has been intensively studied for different regions and climates across the world. In regions where winter processes such as snowfall and melting play a significant role, anticipated changes in temperature might significantly affect hydrological systems. To address this impact, modifications have been made to the fully integrated surface-subsurface flow model HydroGeoSphere (HGS) to allow the simulation of snow accumulation and melting. The modified HGS model was used to assess the potential impact of climate change on surface and subsurface flow in the Saint-Charles River catchment, Quebec (Canada) for the period 2070 to 2100. The model was first developed and calibrated to reproduce observed streamflow and hydraulic heads for current climate conditions. The calibrated model was then used with three different climate scenarios to simulate surface flow and groundwater dynamics for the 2070 to 2100 period. Winter stream discharges are predicted to increase by about 80, 120, and 150% for the three scenarios due to warmer winters, leading to more liquid precipitation and more snowmelt. Conversely, the summer stream discharges are predicted to fall by about 10, 15, and 20% due to an increase in evapotranspiration. However, the annual mean stream discharge should remain stable (±0.1 m³/s). The predicted increase in hydraulic heads in winter may reach 15 m and the maximum decrease in summer may reach 3 m. Simulations show that winter processes play a key role in the seasonal modifications anticipated for surface and subsurface flow dynamics.     

Impact of climate change on water resources in Yongdam Dam Basin,Korea

The main purpose of this study is to investigate and evaluate the impact of climate change on the runoff and water resources of Yongdam basin, Korea. First, we construct global climate change scenarios using the YONU GCM control run and transient experiments, then transform the YONU GCM grid-box predictions with coarse resolution of climate change into the site-specific values by statistical downscaling techniques. The downscaled values are used to modify the parameters of a stochastic weather generator model for the simulation of the site-specific daily weather time series. The weather series is fed into a semi-distributed hydrological model called SLURP to simulate the streamflows associated with other water resources for the condition of 2CO₂. This approach is applied to the Yongdam dam basin in the southern part of Korea. The results show that under the condition of 2CO₂, about 7.6% of annual mean streamflow is reduced when it is compared with the current condition. Seasonal streamflows in the winter and autumn are increased, while streamflow in the summer is decreased. However, the seasonality of the simulated series is similar to the observed pattern An erratum to this article can be found at     

Evaluation of basin storage–discharge sensitivity in Taiwan using low‐flow recession analysis

Sensitivity analysis of the hydrological behaviour of basins has mainly focused on the correlation between streamflow and climate, ignoring the uncertainty of future climate and not utilizing complex hydrological models. However, groundwater storage is affected by climatic change and human activities. The streamflow of many basins is primarily sourced from the natural discharge of aquifers in upstream regions. The correlation between streamflow and groundwater storage has not been thoroughly discussed. In this study, the storage–discharge sensitivity of 22 basins in Taiwan was investigated by means of daily streamflow and rainfall data obtained over more than 30 years. The relationship between storage and discharge variance was evaluated using low‐flow recession analysis and a water balance equation that ignores the influence of rainfall and evapotranspiration. Based on the obtained storage–discharge sensitivity, this study explored whether the water storage and discharge behaviour of the studied basins is susceptible to climate change or human activities and discusses the regional differences in storage–discharge sensitivity. The results showed that the average storage–discharge sensitivities were 0.056 and 0.162 mm^?1 in the northern and southern regions of Taiwan, respectively. In the central and eastern regions, the values were both 0.020 mm^?1. The storage–discharge sensitivity was very high in the southern region. The regional differences in storage–discharge sensitivity with similar climate conditions are primarily due to differences in aquifer properties. Based on the recession curve, other factors responsible for these differences include land utilization, land coverage, and rainfall patterns during dry and wet seasons. These factors lead to differences in groundwater recharge and thus to regional differences in storage–discharge sensitivity.     

A 477‐year dendrohydrological assessment of drought severity for Tsable River,Vancouver Island,British Columbia,Canada

Summer streamflow droughts are becoming more severe in many watersheds on Vancouver Island, British Columbia, as a result of climate warming. Small coastal basins that are the primary water source for most communities and essential to Pacific salmon populations have been particularly affected. Because the most extreme naturally occurring droughts are rarely captured within short instrumental records water managers likely underestimate, and are unprepared for, worst‐case scenario low flows. To provide a long‐term perspective on recent droughts on Vancouver Island, we developed a 477‐year long dendrohydrological reconstruction of summer streamflow for Tsable River based on a network of annual tree‐ring width data. A novel aspect of our study is the use of conifer trees that are energy limited by spring snowmelt timing. Explaining 63% of the instrumental streamflow variability, to our knowledge the reconstruction is the longest of its kind in British Columbia. We demonstrate that targeting the summer streamflow component derived from snowmelt is powerful for determining drought‐season discharge in hybrid runoff regimes, and we suggest that this approach may be applied to small watersheds in temperate environments that are not usually conducive to dendrohydrology. Our findings suggest that since 1520, 21 droughts occurred that were more extreme than recent ‘severe’ events like those in 2003 and 2009. Recent droughts are therefore not anomalous relative to the ~400‐year pre‐instrumental record and should be anticipated within water management strategies. In coming decades, worst‐case scenario natural droughts compounded by land use change and climate change could result in droughts more severe than any since 1520. The influence of the Pacific Decadal Oscillation on instrumental and modelled Tsable River summer streamflow is likely linked to the enhanced role of snowmelt in determining summer discharge during cool phases. Copyright © 2015 John Wiley & Sons, Ltd.     

Impacts of environmental stressors on the water resources of intensively managed hydrologic systems

Watersheds are complex systems due to their surface and subsurface spatially connected water fluxes and biochemical processes that shape Earth's critical zone. In intensively managed landscapes, the implementation of watershed management practices (WMPs) regulate their short‐term responses, whereas climate variability controls the long‐term processes. Understanding their responses to anthropogenic and natural stressors requires a holistic approach that takes into account their multiscale spatio‐temporal linkages. The objective of this study was to simulate the impacts of spatially and temporally varying WMPs and projected climate changes on the surface and groundwater resources in the Upper Sangamon River Basin (USRB), a watershed in central Illinois greatly impacted by agricultural and industrial operations. The physically based hydrologic model MIKE‐SHE was used to simulate the hydrologic responses of the basin to different WMPs and climatic conditions. The simulation of a WMP was varied spatially across the basin to determine the spectrum of responses and critical conditions. In general, the wetlands and forested riparian buffer scenarios were found to cause a reduction in the average streamflow, whereas crop rotation had varied responses depending on the location of implementation and the climate condition assumed. Reductions of up to 30% in the average streamflow were found for the forested riparian buffer under the ESM 2M climate projections, whereas an increase of up to 13% with the crop rotation schemes under CM3 climate was predicted. The model results showed that the installation of tile drains across the USRB increased the water table depth (from ground level) by up to 56%, making crop production possible. Groundwater level in USRB appeared to be more sensitive to future climatic conditions than to WMP implementation. The impacts of WMPs are determined to depend on the climate conditions under which they are applied. Investigating individual and combined stressors' effects over the critical zone at a watershed scale can lead to a more comprehensive analysis of the risk and trade‐offs in every managerial decision that will enable an efficient use of resources.     

Space–time changes in hydrological processes in response to human activities and climatic change in the south China

Due to the influence of climate change and human activities, more and more regions around the world are nowadays facing serious water shortages. This is particularly so with the Guangdong province, an economically prosperous region in China. This study aims at understanding the abrupt behavior of hydrological processes by analyzing monthly precipitation series from 257 rain gauging stations and monthly streamflow series from 25 hydrological stations using the likelihood ratio statistic and schwarz information criterion (SIC). The underlying causes of the changing properties of hydrological processes are investigated by analyzing precipitation changes and information of water reservoirs. It is found that (1) streamflow series in dry season seems to exhibit abrupt changes when compared to that in the flood season; (2) abrupt changes in the values of mean and variance of hydrological variables in the dry season are more common than those in the streamflow series in the flood season, which implies that streamflow in the dry season is more sensitive to human activities and climate change than that in the flood season; (3) no change points are identified in the annual precipitation and precipitation series in the flood season. Annual streamflow and streamflow in the flood season exhibit no abrupt changes, showing the influence of precipitation on streamflow changes in the flood season. However, streamflow changes in the dry season seem to be heavily influenced by hydrological regulations of water reservoirs. The results of this study are of practical importance for regional water resource management in the Guangdong province.     

A spatially distributed model for assessment of the effects of changing land use and climate on urban stream quality

While the effects of land use change in urban areas have been widely examined, the combined effects of climate and land use change on the quality of urban and urbanizing streams have received much less attention. We describe a modelling framework that is applicable to the evaluation of potential changes in urban water quality and associated hydrologic changes in response to ongoing climate and landscape alteration. The grid‐based spatially distributed model, Distributed Hydrology Soil Vegetation Model‐Water Quality (DHSVM‐WQ), is an outgrowth of DHSVM that incorporates modules for assessing hydrology and water quality in urbanized watersheds at a high‐spatial and high‐temporal resolution. DHSVM‐WQ simulates surface run‐off quality and in‐stream processes that control the transport of non‐point source pollutants into urban streams. We configure DHSVM‐WQ for three partially urbanized catchments in the Puget Sound region to evaluate the water quality responses to current conditions and projected changes in climate and/or land use over the next century. Here, we focus on total suspended solids (TSS) and total phosphorus (TP) from non‐point sources (run‐off), as well as stream temperature. The projection of future land use is characterized by a combination of densification in existing urban or partially urban areas and expansion of the urban footprint. The climate change scenarios consist of individual and concurrent changes in temperature and precipitation. Future precipitation is projected to increase in winter and decrease in summer, while future temperature is projected to increase throughout the year. Our results show that urbanization has a much greater effect than climate change on both the magnitude and seasonal variability of streamflow, TSS and TP loads largely because of substantially increased streamflow and particularly winter flow peaks. Water temperature is more sensitive to climate warming scenarios than to urbanization and precipitation changes. Future urbanization and climate change together are predicted to significantly increase annual mean streamflow (up to 55%), water temperature (up to 1.9 °C), TSS load (up to 182%) and TP load (up to 74%). Copyright © 2016 John Wiley & Sons, Ltd.     

Shortening the recurrence periods of extreme water levels under future sea-level rise

Sea-level rise, as a result of global warming, may lead to more natural disasters in coastal regions where there are substantial aggregations of population and property. Thus, this paper focuses on the impact of sea-level rise on the recurrence periods of extreme water levels fitted using the Pearson type III (P-III) model. Current extreme water levels are calculated using observational data, including astronomical high tides and storm surges, while future extreme water levels are determined by superposing scenario data of sea-level rise onto current extreme water levels. On the basis of a case study using data from Shandong Province, China, results indicated that sea-level rise would significantly shorten the recurrence periods of extreme water levels, especially under higher representative concentration pathway (RCP) scenarios. Results showed that by the middle of the century, 100-year current extreme water levels for all stations would translate into once in 15–30 years under RCP 2.6, and once in ten to 25 years under RCP 8.5. Most seriously, the currently low probability event of a 1000-year recurrence would become common, occurring nearly every 10 years by 2100, based on projections under RCP 8.5. Therefore, according to this study, corresponding risk to coastlines could well be increase in future, as the recurrence periods of extreme water levels would be shortened with climate change.     

Water and carbon fluxes of European ecosystems: an evaluation of the ecohydrological model RHESSys

This study investigated whether the regional hydro-ecological simulation system RHESSys is a suitable tool for long-term global change impact studies under selected climatic conditions of Europe, taking advantage of the strongly varying climate along elevational gradients in mountain regions. We performed a validation of RHESSys using daily, monthly and yearly data on (1) streamflow and snow cover in five Alpine catchments and (2) water and carbon fluxes at 15 EUROFLUX sites. The simulation results generally agreed well with observations. RHESSys reasonably reproduced daily and monthly streamflow, as well as the seasonal cycle and amplitude of typical Alpine discharge regimes. Furthermore, RHESSys was capable of capturing the key features of the carbon cycle of various forested ecosystems, including significant differences between managed and close-to-natural forests, and more subtle distinctions between coniferous and deciduous systems. Our analyses confirmed that RHESSys is a suitable tool for studying global change impacts on mountain hydrology. Regarding the simulation of the carbon cycle, this investigation detected some data and model limitations that are discussed in detail. Finally, suggestions for model improvements are made, mainly concerning the formulations of decomposition and respiration rates in biogeochemical models. Copyright © 2006 John Wiley & Sons, Ltd.     

Individual and combined effects of land use/cover and climate change on Wolf Bay watershed streamflow in southern Alabama

Land use/cover (LULC) and climate change are two main factors affecting watershed hydrology. In this paper, individual and combined impacts of LULC and climate change on hydrologic processes were analysed applying the model Soil and Water Assessment Tool in a coastal Alabama watershed in USA. Temporally and spatially downscaled Global Circulation Model outputs predict a slight increase in precipitation in the study area, which is also projected to experience substantial urban growth in the future. Changes in flow frequency and volume in the 2030s (2016–2040) compared to a baseline period (1984–2008) at daily, monthly and annual time scales were explored. A redistribution of daily streamflow is projected when either climate or LULC change was considered. High flows are predicted to increase, while low flows are expected to decrease. Combined change effect results in a more noticeable and uneven distribution of daily streamflow. Monthly average streamflow and surface runoff are projected to increase in spring and winter, but especially in fall. LULC change does not have a significant effect on monthly average streamflow, but the change affects partitioning of streamflow, causing higher surface runoff and lower baseflow. The combined effect leads to a dramatic increase in monthly average streamflow with a stronger increasing trend in surface runoff and decreasing trend in baseflow. Copyright © 2013 John Wiley & Sons, Ltd.