Hattermann et al. 2012) published in scientific journals potential effects of climate
change in river flow regime have been examined. Most studies apply a hydrological
catchment model which is driven by scenario climate data from regional climate
models (dynamical or statistical) and adjusted for the investigation area
(Bates et al. 2008). In the framework of the HABIT-CHANGE project the
eco-hydrological watershed model SWIM (Soil and Water Integrated Model)
(Krysanova et al. 1998) has been chosen to evaluate the impacts of climate change
on eco-hydrological processes and water resources at a regional level provided by
the Potsdam Institute for Climate Impact Research. SWIM is a continuous-time,
semi-distributed watershed model, which combines hydrological processes, vegetation, erosion and nutrient dynamics at the meso- to macro-scale. After validation
for the target areas, the model is used to transform changes in climate and land use
into spatially distributed changes in hydrology and water resources under scenario
conditions. Depending on the physiogeographical and hydrogeological characteristics, different river basins respond in different ways to the same change in climatic
conditions. Uncertainties in projected changes in the hydrological system arise
from internal variability of the climate system, uncertainties in future greenhouse
gas and aerosol emissions, the translation of these emissions into climate change
impacts by global climate models, regionalisation by regional climate models,
hydrological model uncertainty and uncertainties in model input data (e.g. runoff,
soil and land use data). Specific challenges in hydrological modelling are the scale
difference between the climate and hydrological systems, data limitations and the
effect of human interventions such as reservoir impoundment. However, modelling
results can help to locate and assess possible future changes taking into account the
range of uncertainty (different scenarios and models).
Changes in annual river runoff are projected to vary significantly across Europe,
related to regional environmental settings and local changes in precipitation and
temperature. Furthermore, changes in seasonal runoff regime and interannual
runoff variability due to climate change depend primarily on changes in the amount
and timing of precipitation, the evaporative demand and whether precipitation falls
as snow or rain. Generally, annual river flows have been observed to slightly
increase in the north and north-eastern part of Europe and to decrease in the south
and south-eastern parts. Additionally, climate change leads to changes in the
seasonality of river flows, particularly with a trend to lower flows in summer and
higher flows in the winter months (EEA 2008, 2009).
A very robust finding of hydrological impact studies is that in snow-dominated
watersheds warming would lead to changes in seasonality of river flows (Bates
et al. 2008). Hence, spring flow tends to decrease in some areas as a result of
reduced and earlier snowmelt and, in addition, winter flow increases by less winter
precipitation falling as snow which can be stored. In some areas this effect could be
diminished by a general increase in winter precipitation, even if the ratio of snow
related to the total amount decreases. Summer flow in river basins with considerable groundwater contribution will change in accordance with changes in precipitation during the groundwater recharge period in winter. In regions with little or no
36
J. Stagl et al.
change in river flow regime have been examined. Most studies apply a hydrological
catchment model which is driven by scenario climate data from regional climate
models (dynamical or statistical) and adjusted for the investigation area
(Bates et al. 2008). In the framework of the HABIT-CHANGE project the
eco-hydrological watershed model SWIM (Soil and Water Integrated Model)
(Krysanova et al. 1998) has been chosen to evaluate the impacts of climate change
on eco-hydrological processes and water resources at a regional level provided by
the Potsdam Institute for Climate Impact Research. SWIM is a continuous-time,
semi-distributed watershed model, which combines hydrological processes, vegetation, erosion and nutrient dynamics at the meso- to macro-scale. After validation
for the target areas, the model is used to transform changes in climate and land use
into spatially distributed changes in hydrology and water resources under scenario
conditions. Depending on the physiogeographical and hydrogeological characteristics, different river basins respond in different ways to the same change in climatic
conditions. Uncertainties in projected changes in the hydrological system arise
from internal variability of the climate system, uncertainties in future greenhouse
gas and aerosol emissions, the translation of these emissions into climate change
impacts by global climate models, regionalisation by regional climate models,
hydrological model uncertainty and uncertainties in model input data (e.g. runoff,
soil and land use data). Specific challenges in hydrological modelling are the scale
difference between the climate and hydrological systems, data limitations and the
effect of human interventions such as reservoir impoundment. However, modelling
results can help to locate and assess possible future changes taking into account the
range of uncertainty (different scenarios and models).
Changes in annual river runoff are projected to vary significantly across Europe,
related to regional environmental settings and local changes in precipitation and
temperature. Furthermore, changes in seasonal runoff regime and interannual
runoff variability due to climate change depend primarily on changes in the amount
and timing of precipitation, the evaporative demand and whether precipitation falls
as snow or rain. Generally, annual river flows have been observed to slightly
increase in the north and north-eastern part of Europe and to decrease in the south
and south-eastern parts. Additionally, climate change leads to changes in the
seasonality of river flows, particularly with a trend to lower flows in summer and
higher flows in the winter months (EEA 2008, 2009).
A very robust finding of hydrological impact studies is that in snow-dominated
watersheds warming would lead to changes in seasonality of river flows (Bates
et al. 2008). Hence, spring flow tends to decrease in some areas as a result of
reduced and earlier snowmelt and, in addition, winter flow increases by less winter
precipitation falling as snow which can be stored. In some areas this effect could be
diminished by a general increase in winter precipitation, even if the ratio of snow
related to the total amount decreases. Summer flow in river basins with considerable groundwater contribution will change in accordance with changes in precipitation during the groundwater recharge period in winter. In regions with little or no
36
J. Stagl et al.