In this study, we applied a multi-objective calibration approach to select a group of best performing parameter sets for the Variable Infiltration Capacity (VIC) model in the Boulder Creek Watershed, USA. We specifically applied 16 non-dominated parameter sets to simulate hydrologic variables, including streamflow (Q), evapotranspiration (ET) and soil moisture (SM) in two future phases (Phase 1: 2040–2069; Phase 2: 2070–2099). Relative to the historical period, Q and ET increased, and SM decreased. The magnitude of change was greater in Phase 2 than in Phase 1 for both ET (+19.7 per cent) and SM (-5.4 per cent). We found that the model calibration resultant parameter uncertainty could lead to a reversal of the change sign of annual Q during Phase 2. The uncertainty resulting from model calibration was up to 4.3 per cent and 19.6 per cent at the annual and monthly scales, respectively. Seasonally, uncertainty reached the highest levels during the spring snowmelt runoff period between February and May for Q and SM, and during the summer months for ET. These results suggest that the use of a single parameter set may yield substantial bias for hydrological projections, and more efforts should be devoted to constraining the model calibration uncertainty to enable effective water resources decision-making.

Vegetation dynamics is a proxy indicator for environmental changes. The spatial and temporal evolution of the satellite derived normalized difference vegetation index (NDVI) is a useful tool to identify environmental risk at large spatial scales. This study aimed to find the vegetation dynamics, land use and ecological risk in Nepal. The NDVI from different satellite products, land use land cover (LULC) change, human footprint pressure (HFP) and climate (i.e., temperature and precipitation) were analysed. The result showed that NDVI has significantly increased with greening in large areas. Spatially, the decreased NDVI was more noticeable in the Trans-Himalayan region. Meanwhile, the spatially averaged temperature has significantly increased at the rate of 0.03°C yr-1 and precipitation decreased by 3.94 mm yr-1 during 1982–2015. The rapid change in climate, land uses and vegetation can alter the ecosystem. The lower temperature in the mountains is a limiting factor for vegetation. Meanwhile, the high temperature in Terai and low precipitation in western and far western regions with lower VCI enhance dryness. Thus, these regions are ecologically fragile. This study of vegetation dynamics, land use, climates and HFP indicates the level of ecological risk in Nepal.

Water erosion is one of most important global environmental problems which has been widely researched but remains poorly understood because of the complexity of its underlying mechanisms driven by interacting environmental factors. Water erosion is highly sensitive to climate change and associated events such as increasing extreme rainfall events and global warming. This chapter provides a comprehensive overview of the research progress on water erosion processes, as well as how they can be influenced by the natural and anthropogenic factors. The main water erosion control practices are introduced, which need better spatial and temporal allocations under future climate risk. We also reviewed the literature that has quantified direct and indirect climate change impacts on water erosion. Future avenues of research might include: deeper investigation of the natural and anthropogenic factors associated with water erosion, high resolution predictions of water erosion at larger scale and evaluation of economic models associated with erosion control practices to help policymakers develop and implement measures to mitigate the impacts of climate change.

Drought is a complex phenomenon with a long-lasting global impact on human society and natural ecosystems suggesting the need for greater attention to its underlaying causes. Here, we evaluated drought conditions in ESK (Ethiopia, Somalia and Kenya) countries of East Africa during 1964–2015. We evaluate the severe droughts that occurred during 1973–1974, 1984–1985 and 2010–2011 in ESK, based on the drought severity levels. Results show that the drought characteristic parameters of drought duration and intensity increase over time, but drought frequency does not. Higher spatial drought trends were observed in large areas of the ESK countries with mean trend values of 0.0064, 0.0028, 0.00064 and -0.00095 yr–1 for SPEI-1, SPEI-3, SPEI-6 and SPEI-12, respectively. The total land area of the ESK under drought was 38–43, 46–80 and 25–46 per cent during 1973–1974, 1984–1985 and 2010–2011, respectively. Dire drought impacts have affected northeastern and southern Ethiopia, eastern Somalia and northeastern Kenya during the drought years. The spatial drought pattern analysis suggests an increase in drought in vulnerable areas which calls for better drought management strategies to reduce the risks on the natural and human systems.

Precipitation elasticity is an efficient index to quantify the sensitivity of streamflow to precipitation changes in watersheds. It provides us with a tool to understand the historical and predicted changes in streamflow, which is key to assess the impact of climate change on water resources. This chapter provides the details of three frequently used methods for estimating precipitation elasticity of streamflow and a case study on the temporal and spatial variability of precipitation elasticity and runoff coefficient in 164 watersheds in China. The precipitation elasticity is estimated by a non-parametric estimator in three periods of interest. The results bring evidence of an association between spatiotemporal patterns of streamflow changes and precipitation changes, which suggest that climatic change is a dominant factor of annual streamflow changes in the investigated watersheds. In most watersheds, the precipitation elasticity of streamflow is larger than 1, indicating that a 1 per cent change in annual precipitation would result in more than a 1 per cent change in annual streamflow. The precipitation elasticity in watersheds with a small runoff coefficient is generally larger than that in watersheds with a large runoff coefficient.

The Lancang-Mekong River Basin (LMRB) is Asia's most important transboundary river. The precipitation-dependent agriculture and the world's largest inland fishery in the basin feed more than 70 million people. Floods are the main natural disasters which pose a serious threat to the local agriculture and human life. In the future, climate change will affect the streamflow and lead to changes in flood events. Based on the GMDF and GCM data, the SPI and the VIC model were used to assess the impact of climate change on streamflow and flood events during the historical (1985–2016) and future periods (2020–2050) in the LMRB. The results show that the LMRB will become more humid in the future and annual precipitation will change from about -2 to 6 per cent under RCP4.5 and RCP8.5. In the future, this basin should experience a higher flood risk, with more flood events and a relative increase in the flood peak and frequency reaching up to +15 and +58 per cent, respectively. This study contributes to improve our understanding of the role of climate change on streamflow and flood events and provides a scientific reference for the development of local water resources management in the LMRB.

Urbanization can cause local climate change including urban heat islands (UHI) and urban rainfall islands (URI). This study examines urban effects on temperature and precipitation (i.e., bias in observational data in urban areas in comparison to rural areas) in southeast China based on daily meteorological data between 1961- 2010. The urbanization levels of observational sites are characterized by continuous indicators (i.e., urban area fraction and population density) in contrast to the traditional approach that classifies sites into urban and rural categories. Statistical correlation coefficients and linear regression models are employed to analyse the relationship between urbanization levels and changes in temperature and precipitation. The results provide empirical evidence of UHI and URI in southeast China. The estimated average change rates of the minimum, mean daily temperatures and the daily temperature range due to urban effects are 0.061, 0.045 and -0.015°C per decade, respectively. While we do not observe any significant urban effect in annual precipitation, densely urbanized areas are prone to heavier extreme precipitation. The results suggest that urbanization increases the maximum daily and 3-day precipitation by about 10.4 and 14.9 millimetres, respectively. We note that the effects of urbanization on temperature and precipitation vary over the seasons.

Agricultural green and blue water uses in China are accounted for based on the H08 hydrological model. The results indicate that green and blue water uses play various roles in different regions of China. Two different time series trends and their associated drivers are highlighted for the period 1981–2010. Phase advance is found in the annual cycle of blue water use in comparison with green water use. An impact assessment shows that blue water use has a considerable impact on the water system, accounting for more than three quarters of renewable water resources in China. In addition, a large amount of non-renewable water is used in northern China.

Urban flooding disasters have increased due to climate change in recent decades. The induced casualties and economic losses are aggravated by intense urbanization. Climate change projections present high confidence in the increase of flood hazard in the future of the twenty-first century. Moreover, population growth and socio-economic development may lead to an increase of vulnerability to flood hazard. In this context, most countries have launched relevant initiatives to mitigate and adapt to urban flooding disaster, in order to improve urban resilience to flood disaster and achieve urban sustainable development goals. Structural, semi-structural and non-structural strategies have been developed and evaluated in the framework of flood risk management. Furthermore, the integrated flood modelling framework has been developed to support the integrated flood risk assessment under a changing environment. Based on projections, urban flood resilience can be estimated and applied to improve the decision-making of flood policy and regulation, and to guide the planning and design of the flood risk management strategy. In this context, this chapter reviews and discusses the natural and anthropogenic drivers of urban flooding, flood risk management in developing and developed countries and the integrated modelling framework of flood risk management.

A better detection of landslide occurrence is critical for disaster prevention and mitigation. Over the past four decades, great achievements have been made, ranging from inventories to mapping, susceptibility analysis to triggering threshold identification. Here, we proposed a model to establish global distributed rainfall thresholds, by linking triggering rainfall with geo-environmental causes related to landslide events. The model was based on multiple linear regression method, to define rainfall thresholds as a function of diverse geo-environmental variables, fitted and validated by a combined and relatively accurate landslide dataset. Results show primarily feasible performances for training and testing datasets, with low mean absolute error (0.22 log(mm)) and a high coefficient of determination (0.67) totally. We further prepared global distributed threshold maps for sub- and multi-daily rainfall durations. They share similar spatial distributions in line with previous research. The normalized rainfall index, defined as the ratio of precipitation amount over distributed rainfall thresholds, can be an index of possible landslide occurrence, that is, regions with a normalized index over 1.0 correspond to high probability. We argue that distributed rainfall threshold models are an improvement of empirical threshold models and susceptibility assessments by considering the interaction between triggering rainfall and geo-environmental causes, and promising for better hazard assessment.

Climate change caused by the increase in regional and global air temperature significantly affects the environment, especially in cold regions. The frozen ground degradation and its environmental consequence in the Tibetan region are reviewed. Model simulations show that air temperature in the Tibetan Plateau will continue to increase by 3.8–4.8°C at the end of this century. From 1981 to 2010, the duration of seasonally frozen ground was shortened, which delayed its start by 3.4 days and ended 9.4 days earlier than normal. The warming phenomenon resulted in degradation of frozen ground and permafrost by 3.3 105 km2 and 1.11 106 km2, respectively. From 2001 to 2015,soil erosion and desert area increased by 1.14 and 1.80 per cent, respectively. This resulted in a reduction of vegetation coverage. In addition, the influence of climate change on highway on the Qinghai–Tibetan Plateau was also caused by frozen ground degradation, soil deformation and thawed settlement. With a large portion of frozen ground degradation in the Qinghai–Tibetan Plateau, long-term field monitoring, remote sensing investigations, model predictions for temperature and frozen soil, and adaptations to environmental change are needed to mitigate the effects of more intense changes expected in the future.

Saltwater intrusion into coastal aquifers menace multiple coastal areas globally, degrading groundwater quality, which poses an important threat to freshwater supply for agricultural, industrial and domestic utilization. Groundwater over-exploitation used to be commonly recognized as the principle factor causing saltwater intrusion, while sea-level rise, intensified storm surges and precipitation change have grown to become important drivers of factors inducing saltwater intrusion as well. In the context of exacerbated human activities such as groundwater over-exploitation due to the ever-increasing water demand because of population growth and economic and social development, as well as sea-level rise and increased frequency and intensity of extreme weather events and warmer temperatures and changing precipitation patterns and regimes resulting from climate change, the phenomenon of saltwater intrusion worldwide has been seriously aggravated recently. A deeper understanding of the theories and multiple pathways of saltwater intrusion, the commonly-used methods to investigate the extent of saltwater intrusion, as well as numerical approaches to assess the impacts of anthropogenic activities and climate change on saltwater intrusion in future are of great importance to mitigate its negative effects.

Water scarcity has become one of the major risks to sustainable development in the Yellow River (YR) basin. This chapter presents a quantitative projection of future water scarcity in the YR basin with the consideration of both climate change and socioeconomic development, and further analysed the effects of adaptive measures (i.e., improvements in water saving techniques and inter-basin water transfer projects) on water scarcity mitigation. Results suggest that water scarcity in the YR basin would be considerably aggravated by an increase in water demand, and water stress index (WSI) and water deficit increase by 57 and 200 per cent in 2010–2050, respectively. The application of improved water saving techniques might contribute to mitigate about 35 and 53 per cent of the WSI and water deficit in 2050, respectively. Inter-basin water transfer projects are expected to reduce water scarcity in the YR basin by decreasing WSI by 16 per cent and water deficit by 19 per cent in 2050. This chapter contributes to the literature on water scarcity in the YR basin under global change and provides recommendations for future water management and sustainable development.