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.

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.

A Web-based planning support tool for sediment management in a meso-scale river basin in Western Central Brazil.

In scope of an IWRM concept for the Federal District, Western Central Brazil we developed a planning support tool, which enables non-experts to test the effects of land-use and land-cover change (LULCC) on landscape processes and landscape functions (LPF) related to sediment generation and retention. For this purpose we developed the web-based tool Letsmap do Brasil. The tool has two principal layers. The upper layer contains information on land use and its effect on LPF, i.e. sediment retention, runoff control, nitrogen loss control and agronomic value. The parameterized relation between land use and LPF is the core of the whole system. For each LPF a value specific to land use has been assigned. A second layer contains information on landscape properties and potentials (LPP), e.g. potential for sediment input in river networks and runoff potential. By linking land use and LPPs the system provides a spatially explicit assessment of effects of LULCC on landscape processes and functions (LPF). Letsmap do Brasil might have two major purposes. (1) It will support decision-making in river basin management and sediment management. By creating their own land-use/cover pattern non-expert users are enabled to test effects of LULCC on LPFs. (2) It will support and train non-experts to participate in decision processes in land-use planning. Because of its high adaptability, transparency, and simple handling Letsmap do Brasil might be used as tool in river basin management and land-use planning.

Testing the indicative value of magnetic susceptibility measurements for concluding on site potentials and risks provoked by fly ash deposition.

The article presents results of testing the indicative value of magnetic susceptibility for fly ash deposition and its effects on forest site properties. Base saturation and concentrations of Ca and Mg were used as indicators for nutrient pools resulting from fly ash deposition. Concentrations of Fe, Al, Mn, Cd and Black Carbon were used as indicators for risks of leaching. The correlation of magnetic susceptibility with concentrations of nutrient, acidic cations, heavy metals, base saturation and Black Carbon was calculated. Additionally, we tested the suitability of magnetic susceptibility as a parameter in a linear regression based model to predict the concentrations of Ca, Mg, Fe, Al, Mn, Cd and Black Carbon. We were able to show a positive correlation between magnetic susceptibility and the selected indicators. In contrast to previous studies, we were also able to demonstrate the suitability of magnetic susceptibility to predict the size of fly ash deposition influenced nutrient pools mainly for humus layers, especially for Oa horizons. The spatial distribution of magnetic susceptibility showed also a positive correlation with regionalized base saturation. However, because of the data base and other factors impacting the measurement and modeling results, some shortcomings of using a linear regression model must be noted. From these results, we concluded that magnetic susceptibility might be a valuable parameter in a multiple regression based approach, but should not be used alone for predicting effects of fly ash deposition.

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.

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.