ADGEO - Latest Articles

Optimal configuration of a micro-earthquake network

Thu, 02 May 2013 00:00:00 +0200

Optimal configuration of a micro-earthquake network

Advances in Geosciences, 34, 33-36, 2013

Author(s): O. Valtonen, M. Uski, A. Korja, T. Tiira, and J. Kortström

This study simulates automatic event detection and location performance of a micro-earthquake network centred around a future power plant site in Finland, Fennoscandian Shield. Simulation of the event location capability is based on a relationship derived between event magnitude and maximum detection distance. Azimuthal coverage and threshold magnitude are computed for different station configurations and the results are presented as contour maps.

An optimal configuration of ten seismograph stations is proposed for further on-site survey. The network fulfils the preconditions of automatic event location capability down to M_L 0.0 and azimuthal coverage better than 180° within 25 km radius from the study site. Annual number of earthquakes (M_L ≥ 0.0) detected by the network is estimated to be 2 and 8 within 25 and 50 km radius from the power plant site.

Seismic noise study for a new seismic station at King Fahd University of Petroleum and Minerals in Saudi Arabia

Tue, 30 Apr 2013 00:00:00 +0200

Seismic noise study for a new seismic station at King Fahd University of Petroleum and Minerals in Saudi Arabia

Advances in Geosciences, 34, 29-32, 2013

Author(s): S. I. Kaka

In this paper, I describe the work undertaken at King Fahd University of Petroleum and Minerals (KFUPM) in Saudi Arabia to select a suitable site for a new broad band seismic station. The new station will be equipped with a 3-component 120 s to 50 Hz Trillium120 broad band seismometer, Taurus 24-bit data acquisition system along with a large LCD to display the waveform data in real-time. The KFUPM community will have an opportunity to observe daily seismic activity in real-time and to monitor/record both regional and teleseismic events. Moreover, students will gain the opportunity to identify P, S, Love, and Rayleigh waves and learn how to locate an earthquake. The station will also play an important role in providing a source of information about seismic activity for the general public. The station is expected to be operational in a few weeks time.

Local magnitude scale in Slovenia

Tue, 30 Apr 2013 00:00:00 +0200

Local magnitude scale in Slovenia

Advances in Geosciences, 34, 23-28, 2013

Author(s): J. Bajc, Ž. Zaplotnik, M. Živčić, and M. Čarman

In the paper a calibration study of the local magnitude scale in Slovenia is presented. The Seismology and Geology Office of the Slovenian Environment Agency routinely reports the magnitudes M_LV of the earthquakes recorded by the Slovenian seismic stations. The magnitudes are computed from the maximum vertical component of the ground velocity with the magnitude equation that was derived some thirty years ago by regression analysis of the magnitudes recorded by a Wood-Anderson seismograph in Trieste and a short period seismograph in Ljubljana. In the study the present single magnitude M_LV equation is replaced by a general form of the Richter local magnitude M_WA equation. The attenuation function and station-component corrections that compensate the local effects near seismic stations are determined from the synthetic Wood-Anderson seismograms of a large data set by iterative least-square method. The data set used consists of approximately 18 000 earthquakes during a period of 14 yr, each digitally recorded on up to 29 stations. The derived magnitude equation is used to make the final comparison between the new M_WA magnitudes and the routinely calculated M_LV magnitudes. The results show good overall accordance between both magnitude equations. The main advantage of the introduction of station-component corrections is the reduced uncertainty of the local magnitude that is assigned to a certain earthquake.

The South Aegean seismological network – HSNC

Tue, 30 Apr 2013 00:00:00 +0200

The South Aegean seismological network – HSNC

Advances in Geosciences, 34, 15-21, 2013

Author(s): G. Hloupis, I. Papadopoulos, J. P. Makris, and F. Vallianatos

In the present work, the installation and the technology applied for the operation of the Hellenic Seismological Network of Crete (HSNC), located in the front of the Hellenic Arc, are presented. The topology, the communication modes (wire and satellite) along with data collection and processing methodologies applied leads to the operation of a new seismological infrastructure in South Aegean, one of the most seismically active regions in Europe.

Improvement of broadband seismic station installations at the Observatoire de Grenoble (OSUG) seismic network

Tue, 30 Apr 2013 00:00:00 +0200

Improvement of broadband seismic station installations at the Observatoire de Grenoble (OSUG) seismic network

Advances in Geosciences, 34, 9-14, 2013

Author(s): M. Langlais, B. Vial, and O. Coutant

We describe in this paper different improvements that were brought to the installation of seismic broadband stations deployed by the Observatoire de Grenoble (OSUG) in the northern French Alps. This work was realized in the frame of a French-Italian ALCOTRA project (RISE), aimed at modernizing the broadband seismic networks across our common border. We had the opportunity with this project to improve some of our seismic recording sites, both in term of sensor installation quality, and in term of reliability. We detail in particular the thermal and barometric protection system that we designed and show its effect on the reduction of long period noise above 20 s.

OGS improvements in the year 2011 in running the Northeastern Italy Seismic Network

Tue, 30 Apr 2013 00:00:00 +0200

OGS improvements in the year 2011 in running the Northeastern Italy Seismic Network

Advances in Geosciences, 34, 5-8, 2013

Author(s): P. L. Bragato, D. Pesaresi, A. Saraò, P. Di Bartolomeo, and G. Durì

The Centro di Ricerche Sismologiche (CRS, Seismological Research Center) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS (Italian National Institute for Oceanography and Experimental Geophysics) in Udine (Italy) after the strong earthquake of magnitude Mw = 6.4 occurred in 1976 in the Italian Friuli-Venezia Giulia region, started to operate the Northeastern Italy Seismic Network: it currently consists of 12 very sensitive broad band and 21 simpler short period seismic stations, all telemetered to and acquired in real time at the OGS-CRS data centre in Udine. Real time data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of 93 seismic stations acquired in real time, which makes the OGS the reference institute for seismic monitoring of Northeastern Italy, as shown in Fig. 1 (Bragato et al., 2011; Saraò et al., 2010). Since 2002 OGS-CRS is using the Antelope software suite as the main tool for collecting, analyzing, archiving and exchanging seismic data, initially in the framework of the EU Interreg IIIA project "Trans-national seismological networks in the South-Eastern Alps" (Bragato et al., 2010; Pesaresi et al., 2008). SeisComP is also used as a real time data exchange server tool. In order to improve the seismological monitoring of the Northeastern Italy area, at OGS-CRS we tuned existing programs and created ad hoc ones like: a customized web server named PickServer to manually relocate earthquakes, a script for automatic moment tensor determination, scripts for web publishing of earthquake parametric data, waveforms, state of health parameters and shaking maps, noise characterization by means of automatic spectra analysis, and last but not least scripts for email/SMS/fax alerting. A new OGS-CRS real time seismological website (http://rts.crs.inogs.it/) has also been operative since several years.

EGU2012 SM1.3/GI1.7 session: "Improving seismic networks performances: from site selection to data integration"

Tue, 30 Apr 2013 00:00:00 +0200

EGU2012 SM1.3/GI1.7 session: "Improving seismic networks performances: from site selection to data integration"

Advances in Geosciences, 34, 1-4, 2013

Author(s): D. Pesaresi and F. Vernon

The number and quality of seismic stations and networks in Europe continually improves, nevertheless there is always scope to optimize their performance. In this session we welcome contributions from all aspects of seismic network installation, operation and management. This includes site selection; equipment testing and installation; planning and implementing communication paths; policies for redundancy in data acquisition, processing and archiving; and integration of different datasets including GPS and OBS.

Climate trends and projections for the Andean Altiplano and strategies for adaptation

Tue, 02 Apr 2013 00:00:00 +0200

Climate trends and projections for the Andean Altiplano and strategies for adaptation

Advances in Geosciences, 33, 69-77, 2013

Author(s): C. Valdivia, J. Thibeault, J. L. Gilles, M. García, and A. Seth

Climate variability and change impact production in rainfed agricultural systems of the Bolivian highlands. Maximum temperature trends are increasing for the Altiplano. Minimum temperature increases are significant in the northern region, and decreases are significant in the southern region. Producers' perceptions of climate hazards are high in the central region, while concerns with changing climate and unemployment are high in the north. Similar high-risk perceptions involve pests and diseases in both regions. Altiplano climate projections for end-of-century highlights include increases in temperature, extreme event frequency, change in the timing of rainfall, and reduction of soil humidity. Successful adaptation to these changes will require the development of links between the knowledge systems of producers and scientists. Two-way participatory approaches to develop capacity and information that involve decision makers and scientists are appropriate approaches in this context of increased risk, uncertainty and vulnerability.

Evaluation of the current state of small pelagic fisheries in the Colombian Pacific: ensuring the sustainability of the resource and evaluating its response to climatic events

Tue, 02 Apr 2013 00:00:00 +0200

Evaluation of the current state of small pelagic fisheries in the Colombian Pacific: ensuring the sustainability of the resource and evaluating its response to climatic events

Advances in Geosciences, 33, 63-68, 2013

Author(s): L. A. Zapata, B. S. Beltrán-León, J. C. Herrera, P. Jiménez-Tello, L. M. Prieto, R. A. Baos, C. Guevara-Fletcher, and E. Zambrano

Commercial fishing of small pelagic species in Colombia, mainly "carduma" (Cetengraulis mysticetus) and "plumuda" (Opisthonema spp.), has been recorded since 1970. Both are used to produce fish meal for aquaculture and poultry and for canned foods. These two species are filter feeders, and therefore support higher levels of the food chain (other fish, birds and marine mammals), and artisanal fishermen use them as bait. Between 2005 and 2010, 86.131 t have been captured (X = 14.355 t yr⁻¹), and a strong reduction was noticed in 2009 (6.969 t). Carduma is considered a total spawning species. However, from 1997 to 2000 and from 2008 to date, atypical reproductive behavior of the species has been observed, including partition of the spawning period and the reduction of the volume of eggs and larvae released to the environment. Both situations are linked to thermal anomalies such as El Niño and La Niña events. Therefore, the process of assigning the global quota of extraction has been revised to take into account the reduction of total capture during the last years and the inconsistencies of the reproductive processes. The Ministry of Agriculture reduced the quota by 10%, leaving available a total of 27 000 t for 2010 and reduced it again to 25 000 t for 2011. It is important to maintain the management measures that are already implemented on this resource (bans during reproduction seasons, catch quotas, regulation of mesh sizes for the fishing nets, and limiting the number of new vessels) and considering other measures such as season closure for recruitment and establishment of marine protected areas to further contribute to the sustainability of these fisheries.

Rainfall variability related to sea surface temperature anomalies in a Pacific–Andean basin into Ecuador and Peru

Tue, 02 Apr 2013 00:00:00 +0200

Rainfall variability related to sea surface temperature anomalies in a Pacific–Andean basin into Ecuador and Peru

Advances in Geosciences, 33, 53-62, 2013

Author(s): L. Pineda, V. Ntegeka, and P. Willems

The spatiotemporal modes of seasonal rainfall variability and their relation with sea surface temperature anomalies (SSTA 1.2 indices) are examined in the transition from the coastal plain towards the western Andes cordillera in southern Ecuador/northwestern Peru using instrumental records (1970–2000) collected from the Catamayo–Chira basin. A multi-criteria data analysis is conducted within different elevation ranges. The criteria involve rotated principal components, cross correlations and temporal changes of anomalies in rainfall quantiles.

The results confirm that SSTA 1.2 indices influence rainfall variability over the coastal plain (< 510 m a.s.l.) where forcing is dominant within December–May. The El Niño Southern Oscillation also plays a role inland of the coastal plain where a region of ENSO-like rainfall variability is found on the southeastern part of the basin (4°30'–5° S/79°15'–80° W) within March–May (MAM). This suggests that inland distance and elevation are only partial controls of ocean–atmospheric forcing up to ~ 1300 m a.s.l. Our analysis also provides evidence of the SSTA 1.2 indices influence in a large altitudinal range ~ 1400–2700 m a.s.l. confined to the southeastern basin. This region is found consistently perturbed by ENSO within MAM. We conclude that geo-morphological features of the southwestern Ecuadorian Andean ridges play a twofold role in the control of ocean–atmospheric forcing. They can modulate the atmospheric circulation, leading to a dissipation of the signal, or they might favor meteorological processes, leading to enhancement of orographic precipitation. This would explain the observed ENSO signals in instrumental records at locations as high as 2700 m a.s.l.

Seasonal prediction of extreme precipitation events and frequency of rainy days over Costa Rica, Central America, using Canonical Correlation Analysis

Tue, 02 Apr 2013 00:00:00 +0200

Seasonal prediction of extreme precipitation events and frequency of rainy days over Costa Rica, Central America, using Canonical Correlation Analysis

Advances in Geosciences, 33, 41-52, 2013

Author(s): T. Maldonado, E. Alfaro, B. Fallas-López, and L. Alvarado

High mountains divide Costa Rica, Central America, into two main climate regions, the Pacific and Caribbean slopes, which are lee and windward, respectively, according to the North Atlantic trade winds – the dominant wind regime. The rain over the Pacific slope has a bimodal annual cycle, having two maxima, one in May–June and the other in August-September-October (ASO), separated by the mid-summer drought in July. A first maximum of deep convection activity, and hence a first maximum of precipitation, is reached when sea surface temperature (SST) exceeds 29 °C (around May). Then, the SST decreases to around 1 °C due to diminished downwelling solar radiation and stronger easterly winds (during July and August), resulting in a decrease in deep convection activity. Such a reduction in deep convection activity allows an increase in down welling solar radiation and a slight increase in SST (about 28.5 °C) by the end of August and early September, resulting once again in an enhanced deep convection activity, and, consequently, in a second maximum of precipitation. Most of the extreme events are found during ASO. Central American National Meteorological and Hydrological Services (NMHS) have periodic Regional Climate Outlook Fora (RCOF) to elaborate seasonal predictions. Recently, meetings after RCOF with different socioeconomic stakeholders took place to translate the probable climate impacts from predictions. From the feedback processes of these meetings has emerged that extreme event and rainy days seasonal predictions are necessary for different sectors. As is shown in this work, these predictions can be tailored using Canonical Correlation Analysis for rain during ASO, showing that extreme events and rainy days in Central America are influenced by interannual variability related to El Niño-Southern Oscillation and decadal variability associated mainly with Atlantic Multidecadal Oscillation. Analyzing the geographical distribution of the ASO-2010 disaster reports, we noticed that they did not necessarily agree with the geographical extreme precipitation event distribution, meaning that social variables, like population vulnerability, should be included in the extreme events impact analysis.

ENSO impact on hydrology in Peru

Tue, 02 Apr 2013 00:00:00 +0200

ENSO impact on hydrology in Peru

Advances in Geosciences, 33, 33-39, 2013

Author(s): W. S. Lavado-Casimiro, O. Felipe, E. Silvestre, and L. Bourrel

The El Niño and La Niña impacts on the hydrology of Peru were assessed based on discharge data (1968–2006) of 20 river catchments distributed over three drainage regions in Peru: 14 in the Pacific Coast (PC), 3 in the Lake Titicaca (TL) region, and 3 in the Amazonas (AM).

To classify the El Niño and La Niña events, we used the Southern Oscillation Index (SOI) based on hydrological years (September to August). Using the SOI values, the events were re-classified as strong El Niño (SEN), moderate El Niño (MEN), normal years (N), moderate La Niña (MLN) and strong La Niña (SLN).

On average during the SEN years, sharp increases occurred in the discharges in the north central area of the PC and decreases in the remaining discharge stations that were analyzed, while in the years of MEN events, these changes show different responses than those of the SEN. During the years classified as La Niña, positive changes are mostly observed in the majority of the stations in the rivers located in the center of Peru's Pacific Coast. Another important result of this work is that the Ilave River (south of the Titicaca watershed) shows higher positive (negative) impacts during La Niña (El Niño) years, a fact that is not clearly seen in the rivers of the northern part of the Titicaca watershed (Ramis and Huancane rivers).

Influence of different rates of rainfall in the basin of the Uruguay River

Tue, 02 Apr 2013 00:00:00 +0200

Influence of different rates of rainfall in the basin of the Uruguay River

Advances in Geosciences, 33, 27-31, 2013

Author(s): M. Bohrer, B. Zaparoli, and C. B. Saldanha

In the state of Rio Grande do Sul, the rainfall pattern is fairly regular and precipitation is well distributed throughout the year. The aim of this study was to evaluate the spatial and temporal distribution of precipitation in the Uruguay River basin from the determination of homogeneous regions based on the rainfall pattern. Values of 47 meteorological stations of the ANA (National Water Agency) from 1975 to 2005 were used, and values of Pacific sea surface temperature were collected from the National Oceanic and Atmospheric Administration, which is based on observed anomalies for different regions' niños (1 + niño 2, 3 niño, niño 4, niño 3 + 4). From the analysis of the results it was found that the study region showed five homogeneous regions. Knowing the time series of each region, it was possible to verify the regional variability in precipitation, indicating which regions have values above and below the climatological normal, and how the different indexes influence the rainfall pattern in the region.

A multivariate climate index for the western coast of Colombia

Tue, 02 Apr 2013 00:00:00 +0200

A multivariate climate index for the western coast of Colombia

Advances in Geosciences, 33, 21-26, 2013

Author(s): E. Rodríguez-Rubio

Indices of the interannual and interdecadal variability at Tumaco Island (2° N; 79° W; Colombia), based on time series of sea surface temperature (SST), air temperature (AT) and precipitation (P) from a coastal station, are presented regarding the period 1960–2010. These indices are derived from the first two EOF (empirical orthogonal function) modes of the normalized time series, which grasp 84% of the explained variance. The first EOF represents the interannual variability closely correlated with the ENSO-related SST variability of region Niño 1+2 (r = 0.74; lag = 1), Niño 3 (r = 0.71; lag = 1), and the well-known period band 2–8 yr. Furthermore, the first EOF also accounts for the extreme warm events in the eastern equatorial Pacific due to them being well correlated with the E index (r = 0.70). The second EOF represents a much longer variability dominated by the ENSO-like mode or Pacific Decadal Oscillation (PDO), represented by two interdecadal modes (8–16 yr and 20–30 yr), and may account also with moderate warm events and cool events, being more sensitive to cool events.

Enhancement of near-annual variability in the equatorial Pacific in 2000–2008

Tue, 02 Apr 2013 00:00:00 +0200

Enhancement of near-annual variability in the equatorial Pacific in 2000–2008

Advances in Geosciences, 33, 13-19, 2013

Author(s): O. Fashé and B. Dewitte

Like the El Niño Southern Oscillation (ENSO), the near-annual mode is an air–sea coupled mode of the tropical Pacific that can emerge within a relatively cool mean state. It is documented here from satellite observations over the 2000–2008 period based on a covariance analysis between wind stress and zonal current anomalies. It is shown that near-annual variability is enhanced over the last decade. The signature of this mode consists of a zonal seesaw pattern for zonal current with westward (eastward) anomalous currents in the western (eastern) equatorial Pacific. A composite analysis allows identifying the peak and transition phases of this mode, particularly active over 2000–2004. It is suggested that the reduction of the interannual variability in the eastern Pacific over the last decade may be related to the enhancement of the near-annual mode.

Structure of ocean circulation between the Galápagos Islands and Ecuador

Tue, 02 Apr 2013 00:00:00 +0200

Structure of ocean circulation between the Galápagos Islands and Ecuador

Advances in Geosciences, 33, 3-12, 2013

Author(s): C. Collins, A. Mascarenhas, and R. Martinez

From 27 March to 5 April 2009, upper ocean velocities between the Galápagos Islands and Ecuador were measured using a vessel mounted ADCP. A region of possible strong cross-hemisphere exchange was observed immediately to the east of the Galápagos, where a shallow (200 m) 300 km wide northeastward surface flow transported 7–11 Sv. Underlying this strong northeastward surface current, a southward flowing undercurrent was observed which was at least 600 m thick, 100 km wide, and had an observed transport of 7–8 Sv. Next to the Ecuador coast, the shallow (< 200 m) Ecuador Coastal Current was observed to extend offshore 100 km with strongest flow, 0.33 m s⁻¹, near the surface. Immediately to the west of the Ecuador Coastal Current, flow was directed eastward and southward into the beginnings of the Peru-Chile Countercurrent.

The integral of the surface currents between the Galápagos and Ecuador agreed well with observed sea level differences. Although the correlation of the sea level differences with large scale climate indices (Niño3 and the Southern Oscillation Index) was significant, more than half of the sea level variability was not explained. Seasonal variability of the sea level difference indicated that sea level was 2 cm higher at the Galápagos during late winter and early spring, which could be associated with the pattern of northward surface flows observed by R/V Knorr.

Editorial

Tue, 02 Apr 2013 00:00:00 +0200

Editorial

Advances in Geosciences, 33, 1-1, 2013

Author(s): B. Dewitte, L. Bourrel, and T. Ambrizzi

No abstract available.

Impacts of climate change on the water regime of the Inn River basin – extracting adaptation-relevant information from climate model ensembles and impact modelling

Thu, 20 Dec 2012 00:00:00 +0100

Impacts of climate change on the water regime of the Inn River basin – extracting adaptation-relevant information from climate model ensembles and impact modelling

Advances in Geosciences, 32, 99-107, 2012

Author(s): J. Korck, J. Danneberg, and W. Willems

The Inn River basin is a highly relevant study region in terms of potential hydrological impacts of climate change and cross boundary water management tasks in the Alpine Space. Regional analyses in this catchment were performed within the EU co-funded project AdaptAlp. Objective of the study was to gain scientifically based knowledge about impacts of climate change on the water balance and runoff regime for the Inn River basin, this being fundamental for the derivation of adaptation measures.

An ensemble of regional climate projections is formed by combinations of global and regional climate models on the basis of both statistical and bias-corrected dynamical downscaling procedures. Several available reference climate datasets for the study region are taken into account. As impact model, the process-oriented hydrological model WaSiM-ETH is set up.

As expected, regional climate projections indicate temperature increases for the future in the study area. Projections of precipitation change are less homogenous, especially regarding winter months, though most indicate a decrease in the summer. Hydrological simulation results point towards climate induced changes in the water regime of the study region. The analysis of hydrological projections at both ends of the ensemble bandwidth is a source of adaptation relevant information regarding low-flow and high-flow conditions. According to a "drought-prone scenario", mean monthly low flow could decrease up to −40% in the time frame of 2071–2100. A "high-flow-increase-scenario" points towards an increase in mean monthly high flow in the order of +50% in the winter, whilst showing a decrease in autumn.

Stochastic precipitation modeling using circulation patterns to analyze climate impact on floods

Thu, 20 Dec 2012 00:00:00 +0100

Stochastic precipitation modeling using circulation patterns to analyze climate impact on floods

Advances in Geosciences, 32, 93-97, 2012

Author(s): A. Belli and U. Haberlandt

This paper presents the conditioning of a precipitation model to objectively classified circulation patterns (CP). The application of CPs is considered useful with regards to model accuracy improvement and preparation of a downscaling model by using CPs classified with climate model data. As this study aims to produce rainfall as input for derived flood frequency analyses, the validation focuses on extreme values and precipitation events. The analysis is carried out by modifications of a well tested alternating renewal precipitation model.

A modeling framework to assess water and nitrate balances in the Western Bug river basin, Ukraine

Thu, 20 Dec 2012 00:00:00 +0100

A modeling framework to assess water and nitrate balances in the Western Bug river basin, Ukraine

Advances in Geosciences, 32, 85-92, 2012

Author(s): F. Tavares Wahren, B. Helm, F. Schumacher, T. Pluntke, K.-H. Feger, and K. Schwärzel

The objective of this study was to assess the utility of the eco-hydrological SWAT model (Soil and Water Assessment Tool, Arnold et al., 1998) for representing water balance and nitrate fluxes given limited input and calibration data. The investigated catchment is located in Western Ukraine with an area of approximately 2616 km². Land use is currently dominated by agriculture with significant areas of pasture, and has undergone a high degree of changes in land-use and agricultural practice since the end of the Soviet Union. Model application produced a fitted water balance (calibration: R² = 0.52, NS = 0.46; validation: R² = 0.47, NS = 0.51) and plausible ranges and dynamics of nitrate in stream loadings. Groundwater parameters were found to be highly sensitive. The results indicate that SWAT is an appropriate tool for water resource investigations in the Western Bug catchment, and can provide a useful tool for further eco-hydrologic research in the region (i.e. diffuse pollution impacts).

Climate change impacts on Central Asian water resources

Thu, 13 Dec 2012 00:00:00 +0100

Climate change impacts on Central Asian water resources

Advances in Geosciences, 32, 77-83, 2012

Author(s): M. Malsy, T. Aus der Beek, S. Eisner, and M. Flörke

Central Asia is in large parts dominated by low precipitation and, consequentially, by low water availability. Therefore, changes of natural water resources induced by climate change are of high interest. The aim of this study is to analyse the potential impact of climate change on Central Asian water resources until the end of the 21st century and to point out the main affected regions. Thus, simulations with the large-scale hydrology model WaterGAP3 for the baseline and scenario periods were performed with outputs from three General Circulation Models (GCMs: ECHAM5, IPSL-CM4, and CNRM-CM3) and two IPCC-SRES emission scenarios (A2 and B1). The results show that mean modelled annual water availability increases for all scenarios and GCMs while CNRM-CM3 induces the wettest water situation for the 2085s and ECHAM5 the lowest water availability. Furthermore, robust trends to wetter or dryer conditions could be found for many basins. A seasonal shift of mean modelled water availability could be derived for ECHAM5 which does not show a second peak during summer. The application of daily input data showed no improvement of modelled monthly river discharges for most Central Asian basins compared to monthly input data.

The impact of different elevation steps on simulation of snow covered area and the resulting runoff variance

Thu, 13 Dec 2012 00:00:00 +0100

The impact of different elevation steps on simulation of snow covered area and the resulting runoff variance

Advances in Geosciences, 32, 69-76, 2012

Author(s): J. Bellinger, S. Achleitner, J. Schöber, F. Schöberl, R. Kirnbauer, and K. Schneider

This study analyses the impact of vertical model discretisation on modelling snow covered area and the consequential effects on runoff formation of the semi-distributed water balance model HQsim. Therefore, the parameters relevant for snow modelling are varied within the frame of a uniformly distributed Monte Carlo Simulation (MCS). Since the model is based on the hydrological response unit (HRU) approach, the effect of building the HRUs with different elevation steps (250 m and 500 m) is tested for two alpine catchments. In total 5000 parameter combinations were generated for simulation. The results of modelled snow covered area were compared with thirty MODIS (Moderate Resolution Imaging Spectroradiometer) snow cover maps for the melting periods in 2003–2011. Based on a contingency table the comparisons were evaluated by different skill measures. Finally, the pareto optimal parameter settings of each skill measure were detected. Evaluation of runoff variability within the MCS and their pareto optimal runs show reduced variances of model output resulting from an improved simulation of the snow covered area.

Statistical bias correction of global climate projections – consequences for large scale modeling of flood flows

Tue, 11 Dec 2012 00:00:00 +0100

Statistical bias correction of global climate projections – consequences for large scale modeling of flood flows

Advances in Geosciences, 31, 75-82, 2012

Author(s): S. Eisner, F. Voss, and E. Kynast

General circulation models (GCMs) project an increasing frequency and intensity of heavy rainfall events due to global climate change. This rather holds true for regions that are even expected to experience an overall decrease in average annual precipitation. Consequently, this may be attended by an increasing frequency and magnitude of flood events. However, time series of GCMs show a bias in simulating 20th century precipitation and temperature fields and, therefore, cannot directly be used to force hydrological models in order to assess the impact of the projected climate change on certain components of the hydrological cycle. For a posteriori correction, the so-called delta change approach is widely-used which adds the 30-year monthly differences for temperature or ratios for precipitation of the GCM data to each month of a historic climate data set. As the variability of the climate variables in the scenario period is not transferred, this approach is especially questionable if discharge extremes are to be analyzed. In order to preserve the variability given by the GCM, methods of statistical bias correction are applied. This study aims to investigate the impact of two methods of bias correction, the delta change approach and a statistical bias correction, on the large scale modeling of flood discharges, using the example of 25 macroscale catchments in Europe. The discharge simulation is carried out with the global integrated model WaterGAP3 (Water – Global Assessment and Prognosis). Results show that the two bias correction methods lead to distinctively different trends in future flood flows.

Modeling of water balance response to an extreme future scenario in the Ötztal catchment, Austria

Tue, 11 Dec 2012 00:00:00 +0100

Modeling of water balance response to an extreme future scenario in the Ötztal catchment, Austria

Advances in Geosciences, 32, 63-68, 2012

Author(s): C. Tecklenburg, T. Francke, C. Kormann, and A. Bronstert

The aim of the study was to investigate the impact of climate change on the water balance of the Ötztaler Ache catchment in Tyrol, Austria. For this purpose the conceptual hydrological model HBV-D REG was applied. First, the model was calibrated and validated using current observed climate and discharge data. Second, the calibrated model was applied with reanalysis data. Third, downscaled climate scenarios from 2010 to 2099 served as input data to the HBV-D REG. Thereby two extreme land cover scenarios were considered: for water balance modeling a constant glacier coverage from today and additionally for runoff simulations a complete loss of glaciered area. The downscaled climate data were generated with the expanded downscaling method. Scenario simulations indicated an increase in annual areal temperature by 3.4 °C and a slight decrease in annual areal precipitation by 89 mm in the next one hundred years. According to the hydrological modeling, these climate changes caused an increase in evapotranspiration and a decrease in snow coverage. Furthermore model simulations showed an increase in winter and spring runoff, whereas summer runoff was highly sensitive to glacier coverage and decreased with complete loss of glacier coverage.

SWAT model calibration of a grid-based setup

Tue, 11 Dec 2012 00:00:00 +0100

SWAT model calibration of a grid-based setup

Advances in Geosciences, 32, 55-61, 2012

Author(s): H. Rathjens and N. Oppelt

The eco-hydrological model SWAT (Soil and Water Assessment Tool) is a useful tool to simulate the effects of catchment processes and water management practices on the water cycle. For each catchment some model parameters (e.g. ground water delay time, ground water level) remain constant and therefore are used as constant values; other parameters such as soil types or land use are spatially variable and thus have to be spatially discretized. SWAT setup interfaces process input data to fit the data format requirements and to discretize the spatial characteristics of the catchment area. The primarily used configuration is the sub-watershed discretization scheme. This spatial setup method, however, results in a loss of spatial information which can be problematic for SWAT applications that require a spatially detailed description of the catchment area. At present no SWAT interface is available which provides the management of input and output data based on grid cells. To fill this gap, the authors developed a grid-based model interface.

To perform hydrological studies, the SWAT user first calibrates the model to fit to the environmental and hydrological conditions of the catchment. Compared to the sub-watershed approach, the grid-based setup significantly increases model computation time and hence aggravates calibration according to established calibration guidelines. This paper describes how a conventional set of sub-watershed SWAT parameters can be used to calibrate the corresponding grid-based model. The procedure was evaluated in a sub-catchment of the River Elbe (Northern Germany). The simulation of daily discharge resulted in Nash-Sutcliffe efficiencies ranging from 0.76 to 0.78 and from 0.61 to 0.65 for the calibration and validation period respectively; thus model performance is satisfactory. The sub-watershed and grid configuration simulate comparable discharges at the catchment outlet (R² = 0.99). Nevertheless, the major advantage of the grid-based set-up is an enhanced spatial description of landscape units inducing a more realistic spatial distribution of model output parameters.

Potential climate change impacts on the water balance of subcatchments of the River Spree, Germany

Tue, 11 Dec 2012 00:00:00 +0100

Potential climate change impacts on the water balance of subcatchments of the River Spree, Germany

Advances in Geosciences, 32, 49-53, 2012

Author(s): I. Pohle, H. Koch, and U. Grünewald

Lusatia is considered one of the driest regions of Germany. The climatic water balance is negative even under current climate conditions. Due to global climate change, increased temperatures and a shift of precipitation from summer to winter are expected. Therefore, it is of major interest whether the excess water in winter can be stored and to which extent it is used up on increasing evapotranspiration.

Thus, this study focuses on estimating potential climate change impacts on the water balance of two subcatchments of the River Spree using the Soil and Water Integrated Model (SWIM). Climate input was taken from 100 realisations each of two scenarios of the STatistical Analogue Resampling scheme STAR assuming a further temperature increase of 0 K (scenario A) and 2 K by the year 2055 (scenario B) respectively. Resulting from increased temperatures and a shift in precipitation from summer to winter actual evapotranspiration is supposed to increase in winter and early spring, but to decrease in later spring and early summer. This is less pronounced for scenario A than for scenario B. Consequently, also the decrease in discharge and groundwater recharge in late spring is lower for scenario A than for scenario B. The highest differences of runoff generation and groundwater recharge between the two scenarios but also the highest ranges within the scenarios occur in summer and early autumn. It is planned to estimate potential climate change for the catchments of Spree, Schwarze Elster and Lusatian Neisse.

Hydrological simulation of extreme flood scenarios for operational flood management at the Middle Elbe river

Tue, 11 Dec 2012 00:00:00 +0100

Hydrological simulation of extreme flood scenarios for operational flood management at the Middle Elbe river

Advances in Geosciences, 32, 41-48, 2012

Author(s): M. Helms, J. Ihringer, and R. Mikovec

Operational flood management at the Middle Elbe river requires comprehensive knowledge about the magnitude and characteristics of possible extreme flood events. Since these events are not sufficiently included in available historical records, an extended sample of extreme flood events was generated by hydrological scenario simulation. Present paper emphasises simulations in the German part of the catchment of the Middle Elbe river and introduces the stochastic-conceptual precipitation-runoff model which was developed for this task. After validation of this model and its coupling with the weather forecast model COSMO and hydraulic-numerical models, a set of 25 flood scenarios could be simulated and provided for a planning of flood protection measures. Analysis of simulated scenarios reveal that extreme flood events at the Mulde and Middle Elbe rivers may have a wide spectrum of characteristics and may considerably exceed the magnitude of past flood events (e.g., those of August 2002).

Snow accumulation of a high alpine catchment derived from LiDAR measurements

Tue, 11 Dec 2012 00:00:00 +0100

Snow accumulation of a high alpine catchment derived from LiDAR measurements

Advances in Geosciences, 32, 31-39, 2012

Author(s): K. Helfricht, J. Schöber, B. Seiser, A. Fischer, J. Stötter, and M. Kuhn

The spatial distribution of snow accumulation substantially affects the seasonal course of water storage and runoff generation in high mountain catchments. Whereas the areal extent of snow cover can be recorded by satellite data, spatial distribution of snow depth and hence snow water equivalent (SWE) is difficult to measure on catchment scale. In this study we present the application of airborne LiDAR (Light Detecting And Ranging) data to extract snow depths and accumulation distribution in an alpine catchment.

Airborne LiDAR measurements were performed in a glacierized catchment in the Ötztal Alps at the beginning and the end of three accumulation seasons. The resulting digital elevation models (DEMs) were used to calculate surface elevation changes throughout the winter season. These surface elevation changes were primarily referred to as snow depths and are discussed concerning measured precipitation and the spatial characteristics of the accumulation distribution in glacierized and unglacierized areas. To determine the redistribution of catchment precipitation, snow depths were converted into SWE using a simple regression model. Snow accumulation gradients and snow redistribution were evaluated for 100 m elevation bands.

Mean surface elevation changes of the whole catchment ranges from 1.97 m to 2.65 m within the analyzed accumulation seasons. By analyzing the distribution of the snow depths, elevation dependent patterns were obtained as a function of the topography in terms of aspect and slope. The high resolution DEMs show clearly the higher variation of snow depths in rough unglacierized areas compared to snow depths on smooth glacier surfaces. Mean snow depths in glacierized areas are higher than in unglacierized areas. Maximum mean snow depths of 100 m elevation bands are found between 2900 m and 3000 m a.s.l. in unglacierized areas and between 2800 m and 2900 m a.s.l. in glacierized areas, respectively. Calculated accumulation gradients range from 8% to 13% per 100 m elevation band in the observed catchment. Elevation distribution of accumulation calculated by applying these seasonal gradients in comparison to elevation distribution of SWE obtained from airborne laser scanning (ALS) data show the total redistribution of snow from higher to lower elevation bands.

Revealing both, information about the spatial distribution of snow depths and hence the volume of the snow pack, ALS data are an important source for extensive snow accumulation measurements in high alpine catchments. These information about the spatial characteristics of snow distribution are crucial for calibrating hydrological models in order to realistically compute temporal runoff generation by snow melt.

Bed-load transport modelling by coupling an empirical routing scheme and a hydrological-1-D-hydrodynamic model – case study application for a large alpine valley

Tue, 11 Dec 2012 00:00:00 +0100

Bed-load transport modelling by coupling an empirical routing scheme and a hydrological-1-D-hydrodynamic model – case study application for a large alpine valley

Advances in Geosciences, 32, 23-30, 2012

Author(s): B. Gems, S. Achleitner, M. Plörer, F. Schöberl, M. Huttenlau, and M. Aufleger

Sediment transport in mountain rivers and torrents is a substantial process within the assessment of flood related hazard potential and vulnerability in alpine catchments. Focusing on fluvial transport processes, river bed erosion and deposition considerably affects the extent of inundation. The present work deals with scenario-specific bed-load transport modelling in a large alpine valley in the Austrian Alps. A routing scheme founding on empirical equations for the calculation of transport capacities, incipient motion conditions and drag forces is set up and applied to the case study area for two historic flood events. The required hydraulic data result from a distributed hydrological-1-D-hydraulic model. Hydraulics and bed-load transport are simulated sequentially providing a technically well-founded and feasible methodology for the estimation of bed-load transport rates during flood events.

A weather dependent approach to estimate the annual course of vegetation parameters for water balance simulations on the meso- and macroscale

Tue, 11 Dec 2012 00:00:00 +0100

A weather dependent approach to estimate the annual course of vegetation parameters for water balance simulations on the meso- and macroscale

Advances in Geosciences, 32, 15-21, 2012

Author(s): K. Förster, M. Gelleszun, and G. Meon

In order to simulate long-term water balances hydrologic models have to be parameterized for several types of vegetation. Furthermore, a seasonal dependence of vegetation parameters has to be accomplished for a successful application. Many approaches neglect inter-annual variability and shifts due to climate change. In this paper a more comprehensive approach from literature was evaluated and applied to long-term water balance simulations, which incorporates temperature, humidity and maximum bright sunshine hours per day to calculate a growing season index (GSI). A validation of this threshold-related approach is carried out by comparisons with normalized difference vegetation index (NDVI) data and observations from the phenological network in the state of Lower Saxony. The annual courses of GSI and NDVI show a good agreement for numerous sites. A comparison with long-term observations of leaf onset and offset taken from the phenological network also revealed a good model performance. The observed trends indicating a shift toward an earlier leaf onset of 3 days per decade in the lowlands were reproduced very well. The GSI approach was implemented in the hydrologic model Panta Rhei. For the common vegetation parameters like leaf area index, vegetated fraction, albedo and the vegetation height a minimum value and a maximum value were defined for each land surface class. These parameters were scaled with the computed GSI for every time step to obtain a seasonal course for each parameter. Two simulations were carried out each for the current climate and for future climate scenarios. The first run was parameterized with a static annual course of vegetation parameters. The second run incorporates the new GSI approach. For the current climate both models produced comparable results regarding the water balance. Although there are no significant changes in modeled mean annual evapotranspiration and runoff depth in climate change scenarios, mean monthly values of these water balance components are shifted toward a lower runoff in spring and higher values during the winter months.