Carsten Lorz

Sediments in urban river basins: identification of sediment sources within the Lago Paranoá catchment, Brasilia DF, Brazil - using the fingerprint approach.

The development of effective sediment management strategies is a key requirement in tropical areas with fast urban development, like Brasilia DF, Brazil, because of the limited resources available. Accurate identification and management of sediment sources areas, however, is hampered by the dearth of reliable information on the primary sources of sediment. Few studies have attempted to quantify the source of sediment within fast urbanizing, mixed used, tropical catchments. In this study, statistically verified composite fingerprints and a multivariate mixing model have been used to identify the main land use specific sources of sediment deposited in the artificial Lago Paranoá, Central Brazil. Because of the variability of urban land use types within the Lago Paranoá sub-catchments, the fingerprinting approach was additionally undertaking for the Riacho Fundo sub-catchment. The main contributions from individual source types (i.e. surface materials from residential areas, constructions sites, road deposited sediment, cultivated areas, pasture, farm tracks, woodland and natural gullies) varied between the whole catchment and the Riacho Fundo sub-catchment, reflecting the different proportions of land uses. The sediments deposited in the silting zones of the Lago Paranoá originate largely from urban sources (85 ± 4%). Areas with (semi-) natural vegetation and natural gullies contribute 10 ± 2% of the sediment yield. Agricultural sites have only a minor sediment contribution of about 5 ± 4% within the whole catchment. Within the Riacho Fundo sub-catchment there is a significant contribution from urban (53 ± 4%) source, such as residential areas with semi-detached housings (42 ± 3%) with unpaved roads (12 ± 3%) and construction sites (20 ± 3%) and agricultural areas (31 ± 2%). The relative contribution from land use specific sources to the sediment deposition in the silting zone of the Lago Paranoá demonstrated that most of the sediment is derived from sites with high anthropogenic impact.

Challenges of an integrated water resource management for the Distrito Federal, Western Central Brazil: climate, land-use and water resources

Land-use/cover change (LUCC) and climate change are major controlling factors for water resources in the Distrito Federal in Western Central Brazil. Dynamic LUCC in the region has severe impacts on water resources, while climate changes during the last three decades is thought to have only moderate effects. LUCC affects water quantity mostly during base flow conditions. River basins with substantial expansion of agriculture since the end 1970s show a dramatic decrease of base flow discharge by 40–70%, presumably due to irrigation. In contrast, the effects of urbanization on runoff are less distinct, since factors controlling runoff generation might be more variable. For water quality, we found urban areas to have a strong influence on the parameters CSB, NH4+, and suspended solids. In addition, we assume emerging pollutants, e.g. organic (micro)pollutants, might play a major role in the future. The project IWAS-ÁGUA DF focuses on creating the scientific base to face these problems in frame of an IWRM concept for the region. Results of our study will be a contribution to an IRWM concept for the Distrito Federal and will help to maintain high standards in water supply for the region.

Integrating land management and land-cover classes to assess impacts of land use change on ecosystem services

The paper presents a case study in which land use strategies to mitigate Climate Change effects are developed for a model in Saxony, Germany. In this region, the degree of freedom to respond to Climate Change with land-cover changes is very small. Based on a participatory process, an approach was developed to extend land-cover classes (e.g. forest, agriculture) by land management classes. In this paper, the focus is on the forest management classification. In the discussion with regional actors, four recommendations were identified that must be fulfilled to make land management classes regionally applicable and relevant. They should (1) reflect the effectiveness of management practices to mitigate Climate Change impacts, (2) express different management objectives, (3) show the compatibility with future trends (new crops, new public demands) and (4) provide a link to land-cover data. Finally, 22 mixed land-cover and management classes in forestry and around 30 classes in agriculture could be derived. For a test case on afforestation of agricultural sites the paper demonstrates that a more differentiated look at land management practices instead of land-cover classes helps to improve the understanding of (a) regional potentials to adapt to Climate Change and to mitigate its effects and (b) the impact of sectoral management strategies at landscape level on the provision of ecosystem services.

Geochemical signature and properties of sediment sources and alluvial sediments within the Lago Paranoá catchment, Brasilia DF: A study on anthropogenic introduced chemical elements in an urban river basin

One of the largest urban agglomerations in Brazil is the capital Brasilia and its surrounding area. Due to fast urban sprawl and accelerated land use changes, available water supplies are near their limits. The water supply depends largely on surface water collected in reservoirs. There are increasing concerns regarding water shortages due to sediment aggradations, and of water quality due to geochemical modification of sediments from human activities. The concentration of 18 chemical elements and five sediment properties was analyzed from different potential land-based sediment sources and deposited alluvial sediment within the Lago Paranoà catchment. The goal of this study was to assess the distribution of chemical elements and geochemical/physical properties of potential sediment sources in the Lago Paranoá catchment. Principal component analysis and hierarchical cluster analysis were used to investigate the influence of different land use types on the geochemistry of sediments. Geochemical fingerprints of anthropogenic activities were developed based on the results of the cluster analysis grouping. The anthropogenic input of land use specific geochemical elements was examined and quantified by the calculation of enrichment factors using the local geological background as reference. Through comparison of the geochemical signature of potential sediment sources and alluvial sediments of the Lago Paranoá and sub-catchments, the relative contribution of land use specific sediment sources to the sediment deposition of the main water reservoir were estimated. The existing findings suggest a strong relationship between land use and quantifiable features of sediment geochemistry and indicate that urban land use had the greatest responsibility for recent silting in the Lago Paranoá. This assessment helps to characterize the role of human activities in mixed-used watersheds on sediment properties, and provides essential information to guide management responses towards more effective source-reduction strategies.

Assessing hydrological and provisioning ecosystem services in a case study in Western Central Brazil

IntroductionCurrent land use in the Federal District, Western Central Brazil, causes problems related to the water supply which are linked to the regulation of ecosystem services (ES). In scope of an Integrated Water Resources Management concept, we further developed the web-based planning support tool GISCAME for the Pipiripau river basin case study.MethodsWe introduced analyses on ecosystem potentials in the raster-based tool to assess, in a spatially explicit manner, the scenario impact on water purification, sediment retention, water retention, and provision of food and fodder in order to identify potential pathways for conserving water resources. To demonstrate the method, we assess ES depending on a number of land use/land cover change (LULCC) scenarios.ResultsWe found that a considerable increase of water purification and sediment retention is difficult to achieve with realistic small scale LULCC, mainly because in areas with a low potential to provide hydrological ES and thus with a high demand for sustainable land use, such as native Savanna (Cerrado) and natural forests (Mata), favorable land uses were often already existing. We observed synergies in the response of regulating hydrological ES to LULCC but at the same time also trade-offs with provision of food and fodder.ConclusionsOur findings suggest that further degradation and loss of Cerrado and Mata must be avoided and their restoration should be promoted in order to safeguard water resources. We suggest that restoration measures should be focused on arable land located at steep slopes near surface waters to effectively increase hydrological ES through the marginal reduction of provision services.

How to Support Forest Management in a World of Change: Results of Some Regional Studies

This article presents results of several studies in Middle, Eastern and Southeastern Europe on needs and application areas, desirable attributes and marketing potentials of forest management support tools. By comparing present and future application areas, a trend from sectoral planning towards landscape planning and integration of multiple stakeholder needs is emerging. In terms of conflicts, where management support tools might provide benefit, no clear tendencies were found, neither on local nor on regional level. In contrast, on national and European levels, support of the implementation of laws, directives, and regulations was found to be of highest importance. Following the user-requirements analysis, electronic tools supporting communication are preferred against paper-based instruments. The users identified most important attributes of optimized management support tools: (i) a broad accessibility for all users at any time should be guaranteed, (ii) the possibility to integrate iteratively experiences from case studies and from regional experts into the knowledge base (learning system) should be given, and (iii) a self-explanatory user interface is demanded, which is also suitable for users rather inexperienced with electronic tools. However, a market potential analysis revealed that the willingness to pay for management tools is very limited, although the participants specified realistic ranges of maximal amounts of money, which would be invested if the products were suitable and payment inevitable. To bridge the discrepancy between unwillingness to pay and the need to use management support tools, optimized financing or cooperation models between practice and science must be found.

GIS-based probability assessment of natural hazards in forested landscapes of Central and South-Eastern Europe.

We assessed the probability of three major natural hazards—windthrow, drought, and forest fire—for Central and South-Eastern European forests which are major threats for the provision of forest goods and ecosystem services. In addition, we analyzed spatial distribution and implications for a future oriented management of forested landscapes. For estimating the probability of windthrow, we used rooting depth and average wind speed. Probabilities of drought and fire were calculated from climatic and total water balance during growing season. As an approximation to climate change scenarios, we used a simplified approach with a general increase of pET by 20%. Monitoring data from the pan-European forests crown condition program and observed burnt areas and hot spots from the European Forest Fire Information System were used to test the plausibility of probability maps. Regions with high probabilities of natural hazard are identified and management strategies to minimize probability of natural hazards are discussed. We suggest future research should focus on (i) estimating probabilities using process based models (including sensitivity analysis), (ii) defining probability in terms of economic loss, (iii) including biotic hazards, (iv) using more detailed data sets on natural hazards, forest inventories and climate change scenarios, and (v) developing a framework of adaptive risk management.

Assessment and evaluation of metal contents in sediment and water samples within an urban watershed: an analysis of anthropogenic impacts on sediment and water quality in Central Brazil

The aim of this study was to assess the distribution of metals in sediments and surface water within the Lago Paranoá catchment in Central Brazil, and to evaluate metal enrichments due to anthropogenic activities. Concentrations of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sr, Ti and Zn were analyzed in sediment samples from sediment sources under different land uses, in alluvial sediment profiles, and in water samples. Principal component analysis was used to investigate the impact of different land use types on metal concentrations in source sediments. The anthropogenic impact of different land uses on metal concentrations in sediments was quantified by the calculation of enrichment factors, using the local geological background as reference. The data showed that different anthropogenic activities are related to specific metal enrichments in source and alluvial sediments. Particularly urban areas with high-density block development were characterized by higher enrichments of Cd, Cr, Pb, Sr and Zn compared to the local background values. Sediments from agricultural areas had higher concentrations of Cr, Cu and Ni compared to urban areas, which is caused by higher contents of clay and not due to human impact. The concentrations of Cd, Cr, Cu and Pb in surface water samples of the main rivers discharging into Lago Paranoá were very low. The values of Al, Fe, Mn, Sr and Zn differed between the sub-catchments and showed seasonal variation. Metal concentrations depended substantially on terrestrial inputs from anthropogenic and natural sources. The analysis of effluent water samples indicated that there is a temporary metal input into the lake from the two wastewater treatment plants, which might have caused metal enrichments in sediments and water. The regression analyses showed that there is a strong correlation between metal concentrations in alluvial sediments and corresponding water samples, as well as between metal accumulation in the alluvial sediments and shares of urban areas in the sub-catchment.

Sediment characteristics and sedimentations rates of a small river in Western Central Brazil

The purpose of this study is to characterise the alluvial sediments and to quantify sedimentation rates of a small river system, the Ribeirão do Torto in Central Western Brazil. The study area provides an excellent opportunity to examine the effect of land use on sedimentation rates in the region for the first time and thus contributes to understanding sediment transport processes into water reservoirs (silting). 137Cs, 210Pb and 14C dating techniques were used to estimate natural sedimentation rates and those associated with land use development. Complementary use of physical and chemical analyses of the sediments and contained anthropogenic materials revealed that sedimentation dynamics had varied over time. Natural sedimentation rates are more than ten times lower than in the period since the mid-1950s for the alluvial system of the Ribeirão do Torto. The results indicated that human impact had accelerated the sedimentation dynamics, which resulted in higher sediment quantities and sand content and changes of sediment sources. The variation of sedimentation rates may reflect also several other factors, e.g. natural fluctuation in flow energy or geomorphologic changes within the alluvial system. However, the multiple dating techniques and supplementary interpretation employed in this study show the potential use of radionuclides and soil/sediment parameters to identify changes in sedimentation rate, stream energy and sediment characteristics in floodplains.

Spatial and temporal small-scale variability of nitrogen mobilization in a forest ecosystem with high N deposition in NW-Germany

For conifer stands in NW-Germany with high DIN load (23-35 kg N ha(-1) a(-1)) and a long history of nitrogen export the risk of N mobilization were investigated. Ammonium is the most mobilized N species, pointing towards either conditions not favoring nitrification or, more likely - under the dominant aerobic conditions - a very high amount of ammonium in the forest floor. Independence of net nitrification and net ammonification from each other indicates the existence of two separate systems. The nitrifying system depends very much on biotic conditions - as a function of energy and moisture - and seems not to be directly related to N deposition. In contrast, for the ammonification system (Oe horizon) a correlation with the sum of ammonium deposition three months prior to sampling was found. However, the role of disturbance, i.e. nitrogen export, during the last centuries and the role of recovery of the N balance during the last 150 years is still not clear.