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This paper evaluates the combined impacts of climatic and demographic changes on a multipurpose reservoir system in the Harz mountains in northern Germany. For this purpose, the spatially distributed hydrological model PANTA RHEI was firstly calibrated and validated with gridded observational data. Secondly, the hydrological model was forced with data from two regional climate models. The possibilities and limitations of using current regional climate models as an input for hydrological modelling in very high resolution in space and time were evaluated. Their applicability in reservoir operation optimization on an hourly time step was demonstrated. For an increase in extreme events, indicated by one regional climate model, the impact of an adaptation of operation rules with respect to flood protection on the other uses of the system was assessed. Furthermore, a new method was presented, how economic information from national accounting in combination with demographic scenarios can be used in exposure analysis. The paper ends with a demonstration of the importance of combining the impacts of climatic and demographic change, while developing sound and cost-efficient water resources management strategies for the near and distant future. [ABSTRACT FROM AUTHOR]

Since the late Quaternary Period, the rapid rising of the northeastern Qinghai-Tibetan Plateau has greatly changed the East Asian climate and formed different regional monsoon climates. Various microstructures of the loess in northern China have formed under a variety of climatic conditions. The scanning electron microscope (SEM) and energy spectrum analysis are used in this paper to study the relationship between the indexes of loess microstructures and the forming climates, and the indexes include the diameter of sand grains, Ca/Fe value and the characteristic shapes of the loess from SEM microstructures pictures. In terms of their respective climatic circumstances, the major microstructures of regional loess may be classified into nine categories according to their forms and particle sizes, such as loess formed in near-sand source, loess of granule sand dropping, and loess formed in hot and rainy places, i.e. with the loess SEM pictures, climates of about 15 ka b.p. in different places may be evaluated. In conclusion, the clear and distinguishable loess microstructures and their indexes in the Loess Plateau of China can also deduce the evolution of climate, such as warm or cold and wet or dry, and even sandstorm activities when the loess is deposited. [ABSTRACT FROM AUTHOR]

Based on the data of the Alxa desert region and 27 meteorological stations recorded by 1960-2013, T ≥ 0 and T ≥ 10 °C accumulated temperatures were analyzed by using sliding average, linear regression, Mann-Kendall abrupt change test, and kriging interpolation methods. The results show that the T ≥ 0 °C accumulated temperature increased significantly by 9.94 °C/a and that of the T ≥ 10 °C increased by 8.88 °C/a during 1960-2013. The increases in the eastern study area were the most obvious, followed by those in the western and central regions. Additionally, the trends of these regions were highly consistent with that of the entire study area. The accumulated temperatures in the study area increased modestly prior to the 1980s, after which time a fairly steady climb began during the late 1980s. The two abrupt change points of T ≥ 0 and T ≥ 10 °C were in 1996 and 1998, respectively. Additionally, the accumulated temperatures increased significantly around 2000. The analysis shows that higher accumulated temperature occurred in the Alxa desert region than in the surrounding area. The distribution of increases in T ≥ 0 and T ≥ 10 °C accumulated temperatures around the study area presented varying spatial differentiation. For T ≥ 0 °C accumulated temperature, an increase at the edge of the Tengger desert was the most obvious. T ≥ 10 °C accumulated temperature exhibited a smaller increase than that of T ≥ 0 °C. In addition, the smallest amplitude of temperature increase was measured in the central Alxa desert region and in the surrounding area. [ABSTRACT FROM AUTHOR]

A large-scale numerical flow and transport model was developed for the central-eastern arid part of the Arabian Peninsula. The model was applied to a region with freshwater resources dating back to more humid periods of the past, which are faced with overexploitation today. Model inflow was based on infiltration around wadi beds and groundwater recharge. Inflow was balanced by natural outflows, such as evaporation from sabkhas, spring discharge, and discharge to the sea. Two models were developed: (1) a short-term present-day model to estimate effective model parameters, and (2) a long-term model to study the development of the groundwater resources during the Mid- and Late Holocene and the natural response of the groundwater system to changes in climate. Hydraulic model parameters (hydraulic conductivity and specific storage) were assigned with respect to geological structures. Hydraulic parameters were estimated with an inverse PEST model by calibrating against observed depression cones cause by groundwater abstraction. Sensitivity analysis demonstrated that estimated model parameters were associated with a high uncertainty at a certain distance from agricultural areas when calibration data were lacking. A long-term model starting 10,000 years BP was calibrated by spring discharge and palaeo-groundwater levels and validated using measured C groundwater ages. The long-model predicted that groundwater levels adapted in response to changes in precipitation. During the Mid-Holocene, which was characterized by an intensification of the monsoon season, groundwater levels increased by 10 m on the mainland within the shallow aquifers and adapted quickly to higher recharge rates. The deeper aquifers were less affected by changes in climate. Along the present-day coastline, the groundwater level rose by about 25 m due to the declined sea level in the Mid-Holocene. During this period, surface run-off was possible as groundwater levels temporarily reached the ground surface. The natural groundwater budget reacted sensitively to changes in climate. Between 10 and 3 ka, groundwater storage occurred. During the Late Holocene, at 3 ka, natural depletion of the groundwater system began, which still prevails today. [ABSTRACT FROM AUTHOR]

The water demand in arid regions is commonly covered by groundwater resources that date back to more humid periods of the Pleistocene and Holocene. Within the investigated arid part of SE Saudi-Arabia information about climate, groundwater levels, and pumping rates are only available for regions where groundwater extractions occur at present-day. For the prediction of the impact of long-term climate changes on groundwater resources an understanding of the hydrogeological and hydrological past and the development of the aquifers is necessary. Therefore, all available information about hydrology and hydrogeology for the past 10,000 years BP were collected and compiled to a conceptual model of the aquifer development on the Arabian Peninsula since the last Ice-Age. The climatic history was displayed by changes in precipitation, temperature and recharge during the mid-S and late Holocene. The hydrogeological development is described by groundwater ages, sea level fluctuations, movement of the coastline, and the development of sabkhas. The most sensitive parameter to describe the development of aquifer system is recharge. Present-day recharge was calculated with the hydrological model system HEC-HMS accounting for current precipitation, temperature, wind, soil types, and geomorphology. With respect to changes in precipitation and temperature over the past 10,000 years the temporal and spatial variability of groundwater recharge was calculated using empirical equations valid for semi-arid and arid settings. Further inflow into the groundwater system results from surface water infiltration in wadi beds, while natural outflow from the groundwater system occurs by discharge to the Gulf, evaporation from sabkhas, and spring discharge. Backward predictions can be verified by sedimentological observations of palaeo-river systems and lakes indicating that groundwater levels reached temporarily the surface under wetter climate conditions and C groundwater ages displaying groundwater residence times. [ABSTRACT FROM AUTHOR]

On the basis of the data of glacier mass balance during 1946-2005 over Svalbard, Northern Scandinavia, and Southern Norway, the characteristics of glacier mass-balance are analyzed, and its sensitivity to climate change is calculated using a simple degree-day model. The mass balance of glaciers in these three regions reached maximum or comparatively high values in the late 1980s or the early 1990s. After that there was an accelerating negative tendency. A glacier with more positive mass balance has a higher sensitivity to equilibrium-line altitude (or climate) change and vice versa. On average, the mass loss during the entire period in these three regions was equivalent to the result of an air temperature rise of 0.32°C relative to zero net balance state. The highest temperature increase is found in Svalbard, and is 0.55°C; however, a rise of only 0.12°C is found in Southern Norway. The net balance sensitivity to a hypothetical air temperature increase of +1°C ranges from −0.31 to −1.03 m w.e. a, and the net balance sensitivity to an assumed increase in snow precipitation of +10% varies from +0.05 to +0.37 m w.e. a; thus, a 31% increase in snow precipitation is needed to compensate for the net mass loss induced by an air temperature increase of +1°C. The summer balance sensitivity to a hypothetical air temperature increase of +1°C varies from −0.39 to −0.95 m w.e. a, and the winter balance sensitivity to an assumed increase in snow precipitation of +10% ranges from +0.02 to +0.38 m w.e. a. This study confirms early findings that maritime glaciers have comparatively higher mass balance sensitivity than continental glaciers. [ABSTRACT FROM AUTHOR]