Frankfurt Hydrology Paper
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4
Artificial drainage of agricultural land, for example with ditches or drainage tubes, is used to avoid water logging and to manage high groundwater tables. Among other impacts it influences the nutrient balances by increasing leaching losses and by decreasing denitrification. To simulate terrestrial transport of nitrogen on the global scale, a digital global map of artificially drained agricultural areas was developed. The map depicts the percentage of each 5’ by 5’ grid cell that is equipped for artificial drainage. Information on artificial drainage in countries or sub-national units was mainly derived from international inventories. Distribution to grid cells was based, for most countries, on the "Global Croplands Dataset" of Ramankutty et al. (1998) and the "Digital Global Map of Irrigation Areas" of Siebert et al. (2005). For some European countries the CORINE land cover dataset was used instead of the both datasets mentioned above. Maps with outlines of artificially drained areas were available for 6 countries. The global drainage area on the map is 167 Mio hectares. For only 11 out of the 116 countries with information on artificial drainage areas, sub-national information could be taken into account. Due to this coarse spatial resolution of the data sources, we recommended to use the map of artificially drained areas only for continental to global scale assessments. This documentation describes the dataset, the data sources and the map generation, and it discusses the data uncertainty.
1
The Land and Water Development Division of the Food and Agriculture Organization of the United Nations and the Johann Wolfgang Goethe University, Frankfurt am Main, Germany, are cooperating in the development of a global irrigation-mapping facility. This report describes an update of the Digital Global Map of Irrigated Areas for the continent of Asia. For this update, an inventory of subnational irrigation statistics for the continent was compiled. The reference year for the statistics is 2000. Adding up the irrigated areas per country as documented in the report gives a total of 188.5 million ha for the entire continent. The total number of subnational units used in the inventory is 4 428. In order to distribute the irrigation statistics per subnational unit, digital spatial data layers and printed maps were used. Irrigation maps were derived from project reports, irrigation subsector studies, and books related to irrigation and drainage. These maps were digitized and compared with satellite images of many regions. In areas without spatial information on irrigated areas, additional information was used to locate areas where irrigation is likely, such as land-cover and land-use maps that indicate agricultural areas or areas with crops that are usually grown under irrigation. Contents 1. Working Report I: Generation of a map of administrative units compatible with statistics used to update the Digital Global Map of Irrigated Areas in Asia 2. Working Report II: The inventory of subnational irrigation statistics for the Asian part of the Digital Global Map of Irrigated Areas 3. Working Report III: Geospatial information used to locate irrigated areas within the subnational units in the Asian part of the Digital Global Map of Irrigated Areas 4. Working Report IV: Update of the Digital Global Map of Irrigated Areas in Asia, Results Maps
12
In the past sixty years, excessive water consumption and dam construction have significantly influenced natural flow regimes and surface freshwater ecosystems throughout China, and thus resulted in serious environmental problems. In order to balance the competing water demands between human and environment and provide knowledge on sustainable water management, assessments on anthropogenic flow alterations and their impacts on aquatic and riparian ecosystems in China are needed.
In this study, the first evaluation on quantitative relationships between anthropogenic flow alterations and ecological responses in eleven river basins and watersheds in China was performed based on the data that could be obtained from published case studies. Quantitative relationships between changes in average annual discharge, seasonal low flow and seasonal high flow and changes in ecological indicators (fish diversity, fish catch and vegetation cover, etc.) were analyzed. The results showed that changes in riparian vegetation cover as well as changes in fish diversity and fish catch were strongly correlated with the changes in flow magnitude (r = 0.77, 0.66), especially with changes in average annual river discharge. In addition, more than half of the variations in vegetation cover could be explained by changes in average annual river discharge (r² = 0.63) and roughly 50 % changes in fish catch in arid and semi-arid region and 60% changes of fish catch in humid region could be related to alterations in average annual river discharge (r² = 0.53, 0.58).
In a supplementary analysis of this study, the first estimation on quantitative relationships between decreases in native fish species richness and anthropogenic flow alterations in 34 river basins and sub-basins in China was conducted. Linear relationships between losses of native fish species and five ecologically relevant flow indicators were analyzed by single and multiple regression models. For the single regression analysis, significant linear relationships were detected for the indicators of long-term average annual discharge (ILTA) and statistical low flow Q90 (IQ90). For the multiple regressions, no indicator other than ILTA has significant relationships with changes in number of fish species mainly due to collinearity. Two conclusions emerged from the analysis: 1) losses of fish species were positively correlated with changes in ILTA in China and 2) indicator of ILTA was dominant over other flow indicators included in this research for the given dataset. These results provide a guideline for the sustainable water resources management in rivers with high risk of fish extinction in China.
19
Groundwater is the largest source of accessible freshwater with its dynamics having significantly changed due to human withdrawals, and being projected to continue to as a result of climate change. The pumping of groundwater has led to lowered water tables, decreased base flow, and depletion.
Global hydrological models (GHMs) are used to simulate the global freshwater cycle, assessing impacts of changes in climate and human freshwater use. Currently, groundwater is commonly represented by a bucket-like linear storage component in these models. Bucket models, however, cannot provide information on the location of the groundwater table. Due to this limitation, they can only simulate groundwater discharge to surface water bodies but not recharge from surface water to groundwater and calculate no lateral and vertical groundwater flow whatsoever among grid cells. For instance this may lead to an underestimation of groundwater resources in semiarid areas, where groundwater is often replenished by surface water. In order to overcome these limitations it is necessary to replace the linear groundwater model in GHMs with a hydraulic head gradient-based groundwater flow model
This thesis presents the newly developed global groundwater model G3M and its coupling to the GHM WaterGAP spanning over 70,000 lines of newly developed code. Development and validation of the modeling software are discussed along with numerical challenges. Based on the newly developed software, a global natural equilibrium groundwater model is presented showing better agreements with observations than previous models. Groundwater discharge to rivers is found to be the most dominant flow component globally, compared to flows to other surface water bodies and lateral flows. Furthermore, first global maps of the distribution of gaining and losing surface water bodies are displayed.
For the purpose of determining the uncertainty in model outcomes a sensitivity study is conducted with an innovative approach through applying a global sensitivity analysis for a computationally complex model. First global maps of spatially distributed parameter sensitivities are presented. The results at hand indicate that globally simulated hydraulic heads are equally sensitive to hydraulic conductivity, groundwater recharge and surface water body elevation, even though parameter sensitivities do vary regionally.
A high resolution model of New Zealand is developed to further understand the involved uncertainties connected to the spatial resolution of the global model. This thesis finds that a new understanding is necessary how these models can be evaluated and that a simple increase in spatial resolution is not improving the model performance when compared to observations.
Alongside the assessment of the natural equilibrium, the concept of a fully coupled transient model as integrated storage component replacing the former model in the hydrological model WaterGAP is discussed. First results reveal that the model shows reasonable response to seasonal variability although it contains persistent head trends leading to global overestimates of water table depth due to an incomplete coupling. Nonetheless, WaterGAP-G3M is already able to show plausible long term storage trends for areas that are known to be affected by groundwater depletion. In comparison with two established regional models in the Central Valley the coupled model shows a highly promising simulation of storage declines.
13
Transforming the current rather centralized electricity generating system into a climate neutral system based on renewable energy is an important approach to reduce greenhouse gas emissions and thus mitigate climate change. Stakeholders have each of them their own perception of the best strategies to achieve such a transformation. All perspectives are equally legitimate and needed for developing a specific transformation strategy suited for the region in focus....
10
Die vorliegende Arbeit wurde im Rahmen des Forschungsprojekts „Integrierte Analyse von mobilen, organischen Fremdstoffen in Fließgewässern“ (INTAFERE) am Institut für Physische Geographie an der Goethe-Universität Frankfurt erstellt. In INTAFERE wurde das Gefährdungspotenzial von mobilen, organischen Fremdstoffen (MOF) für aquatische Ökosysteme und die natürlichen Wasserressourcen in integrierter und partizipativer Art und Weise untersucht. MOF sind chemische Substanzen, die in Alltagsprodukten enthalten sind und durch unterschiedliche Eintragsfade in unbekannten Mengen in Oberflächengewässer eingetragen werden. Problematisch sind aus Umweltgesichtspunkten ihre Eigenschaften: sie besitzen im Wasser eine hohe Mobilität und sind schwer abbaubar. Dies führt zu einer Persistenz über lange Zeiträume. Für einige dieser Substanzen wurde zudem gezeigt, dass sie in sehr geringen Konzentrationen biologisch aktiv sind und für aquatische Ökosysteme eine Gefahr darstellen. In INTAFERE wurden drei zentrale Ziele verfolgt: Charakterisierung des Problemfeldes MOF, Erzeugung von praxisrelevantem Wissen für das Management von MOF und Entwicklung einer Softwareanwendung, die gesellschaftliche Aushandlungsprozesse durch eine transparente Darstellung der Wirkungszusammenhänge im Problemfeld unterstützt. Um einen Beitrag für die Erfüllung der Ziele zu leisten, war es die Aufgabe der Verfasserin, eine Akteursanalyse und -modellierung durchzuführen sowie Zukunftsszenarien im Bereich der MOF zu entwickeln. Dafür existierte keine adäquate Methodik, daher verfolgt die Dissertation zum einen die Entwicklung einer Methodik und zum anderen deren Anwendung im Kontext des Projektes INTAFERE. Da im Forschungsprozess die Durchführung von Analysen, die wissenschaftliche und gesellschaftliche Sichtweise der Problematik sowie die Erarbeitung von praktischen Lösungen im Mittelpunkt standen, wurde eine transdisziplinäre Herangehensweise gewählt. Ziel war es, eine Methodik zu entwerfen, die sowohl eine Entwicklung von Szenarien als auch eine Modellierung von Handlungsentscheidungen umfasst. Eine Modellierung und Visualisierung von Handlungsentscheidungen ist notwendig, um Strategien für ein Umweltproblem für verschiedene Szenarien zu ermitteln, und damit einen Lernprozess der Stakeholder zu initiieren. Dies wurde mit der transdisziplinären Methode „Akteursbasierte Modellierung“ umgesetzt. Hierbei wurden insbesondere Aspekte der Problemwahrnehmung von Akteuren und deren Darstellung, der partizipativen Szenarienentwicklung sowie der semi-quantitativen Modellierung von Handlungsentscheidungen berücksichtigt. Die Verfasserin hat mit der semi-quantitativen akteursbasierten Modellierung eine Methode erarbeitet und getestet, die bisher unverbundene Komponenten (wie die Software Dynamic Actor Network Analysis (DANA) und die Szenarienentwicklung) zusammenführt. Um Handlungsentscheidungen unter verschiedenen Szenarien zu modellieren hat die Autorin eine sequentielle Modellierung entwickelt, die mit der Software DANA durchgeführt werden kann. Die dafür notwendige Weiterentwicklung von DANA wurde von Dr. Pieter Bots (TU Delft) umgesetzt. Die akteursbasierte Modellierung läuft in drei methodischen Schritten ab: 1. Modellierung von Akteurs-Sichtweisen in Form von Wahrnehmungsgraphen und deren Analyse, aufbauend auf Ergebnissen von qualitativen, leitfaden-gestützten Expertengesprächen (= Akteursmodellierung), 2. partizipative Szenarienentwicklung mit den Akteuren und 3. Zusammenführung der Ergebnisse der Akteursmodellierung und der Szenarienentwicklung und darauf aufbauend eine sequentielle Modellierung von Handlungsentscheidungen und deren Auswirkungen auf Schlüsselfaktoren. Im Zuge der Anwendung auf das Problemfeld der MOF wurde für folgende Akteure jeweils ein Wahrnehmungsgraph modelliert: Obere Wasserbehörde, Umweltbundesamt, Umwelt- und Verbraucherschutzorganisationen, Wasserversorger sowie für die Hersteller von verschiedenen MOF, weiterhin für die European Flame Retardants Association und die Weiterverarbeitende Industrie. Das Ergebnis der Szenarienentwicklung waren vier Szenarien: ein Gesundheitsszenario, unter der Annahme von hohen lokalen Umweltstandards durch nachhaltigkeitsorientierte KonsumentInnen, ein Umweltszenario, in dem eine starke Regulierung und nachhaltigkeitsorientierter Konsum Hand in Hand gehen, ein Globalisierungsszenario, in dem Wirtschaftsmacht und preisbewusste KonsumentInnen statt staatliche Regulierung vorherrschen und ein Technikszenario, unter der Annahme, dass Kläranlagen, bedingt durch eine starke Regulierung, aufgerüstet werden. Bei der Modellierung von Handlungsentscheidungen wurden die Wahrnehmungsgraphen und die vier Szenarien miteinander verknüpft. Pro Substanz wurde ein Modell entwickelt, welches die wichtigsten Systemkomponenten in einer angemessenen Komplexität umfasst und die von den Akteuren gemeinsam getragene Einschätzung der Wirkungsbeziehungen darstellt. Insgesamt wurden 16 Modelle entwickelt. Basierend auf den simulierten Akteurshandlungen wurden relativen Veränderungen der Schlüsselfaktoren Produktion, Import und Leistungsfähigkeit der Kläranlagen für die vier genannten Szenarien berechnet. In Zusammenarbeit mit Pieter Bots konnten algorithmische Beiträge zur Analyse- und Modellierungssoftware DANA getestet und verbessert werden. Da keine vollständige und zugleich leicht verständliche Einführung zu DANA vorlag, wurde für Nutzer im Rahmen dieser Dissertation eine Anleitung verfasst, die die Modellierung von Wahrnehmungsgraphen und deren Analyse sowie alle Schritte der akteursbasierten Modellierung mit DANA erläutert.
15
Water is scarce in semi-arid and arid regions. Using alternative water sources (i.e. non-conventional water sources), such as municipal reuse water and harvested rain, contributes to using existing water resources more efficiently and productively. The aim of this study is to evaluate the two alternative water sources reuse water and harvested rain for the irrigation of small-holder agriculture from a system perspective. This helps decision and policy makers to have proper information about which system and technology to adopt under local conditions. For this, the evaluation included ecologic, societal, economic, institutional and political as well as technical aspects. For the evaluation, the study area in central-northern Namibia was chosen in the frame of the research and development project CuveWaters. The main methods used include a mathematical material flow analysis, the computation and modelling of crop requirements, a multi-criteria decision analysis using the Analytical Hierarchy Process (AHP) method and a financial cost-benefit analysis. From a systemic perspective, the proposed novel systems were compared to the exciting conventional infrastructure. The results showed that both water reuse and rainwater harvesting systems for the irrigation of small-holder horticulture offer numerous technological, ecologic, economic, societal, institutional and political benefits. Rainwater harvesting based gardens have a positive benefit-cost ratio under favorable conditions. Government programs could fund the infrastructure investment costs, while the micro-entrepreneur can assume a micro-credit to finance operation and maintenance costs. Installing sanitation in informal settlements and reusing municipal water for irrigation reduces the overall water demand of households and agriculture by 39%, compared to improving sanitation facilities in informal settlements without reusing the water for agriculture. Given that water is the limiting factor for crop fertigation, the generated nutrient-rich reuse water is sufficient to annually irrigate about 10 m2 to 13 m2 per sanitation user. Compared to crop nutrient requirements, there are too many nutrients in the reuse water. Thus when using nutrient-rich reuse water, no use of fertilizers and a careful salt management is necessary. When comparing this novel system with improved sanitation, advanced wastewater treatment and nutrient-rich water reuse to the conventional and to two adapted systems, results showed that the novel CuveWaters system is the best option for the given context in a semi-arid developing country. Therefore, the results of this study suggest a further roll-out of the novel CuveWaters system. The methodology developed and the results of this study demonstrated that taking sanitation users into consideration plays a major role for the planning of an integrated water reuse infrastructure because they are the determinant factor for the amount of available nutrient-rich reuse water. In addition, it could be shown that water reuse and rainwater harvesting systems for the irrigation of small-scale gardens provide a wide range of benefits and can be key to using scarce water resources more efficiently and to contributing to the Sustainable Development Goals.
16
The estimation of water balance components as well as water-related indicators on the land surface by means of global hydrological models have evolved in recent decades. Results of such models are frequently used in global- and continental-scale assessments of the current and future state of the terrestrial water cycle and provide a valuable data basis, e.g., for the Intergovernmental Panel on Climate Change. The Water – Global Assessment and Prognosis (WaterGAP) model is one of the state-of-the-art models in that field and has been in development and application for around 20 years. The evaluation, modification and application of WaterGAP is the subject of this thesis. In particular, the sensitivity of climate input data on radiation calculation and simulated water fluxes and storages is evaluated in the first part. Effects of model modification such as updated spatial input datasets, improved process representation or an alternative calibration scheme are the focus of the second part. Finally, three applications of WaterGAP give insight into the capabilities of that model, namely an estimate of global and continental water balance components, an assessment of groundwater depletion and the impact of climate change on river flow regimes. Model experiments, which are described in six journal papers as well as the appendices, were used as the basis for answering the total of 13 research questions. One of the major foci was to quantify the sensitivity of simulated water fluxes and storages to alternative climate input data. It was found that the handling of precipitation undercatch leads to the greatest difference in water balance components, especially in those areas where WaterGAP is not calibrated due to a lack of river discharge observations. The modifications of WaterGAP in the last few decades has led in general to an improved simulation of monthly river discharge, but process representation in semi-arid and arid regions still requires improvements. With the most current model version, WaterGAP 2.2b, and for the time period 1971–2000, river discharge to the oceans and inland sinks is estimated to be 40 000 km3 yr-1, whereas actual evapotranspiration is simulated as 70 500 km3 yr-1. Future research needs for WaterGAP in particular but also for the global hydrological model community in general are defined, promoting a community-driven effort for a robust assessment of the continental water cycle.
11
Bayesian Networks are computer-based environmental models that are frequently used to support decision-making under uncertainty. Under data scarce conditions, Bayesian Networks can be developed, parameterized, and run based on expert knowledge only. However, the efficiency of expert-based Bayesian Network modeling is limited by the difficulty in deriving model inputs in the time available during expert workshops. This thesis therefore aimed at developing a simple and robust method for deriving conditional probability tables from expert estimates in a time-efficient way. The design and application of this new elicitation and conversion method is demonstrated using a case study in Xinjiang, Northwest China. The key characteristics of this method are its time-efficiency and the approach to use different conversion tables based on varying levels of confidence. Although the method has its limitations, e.g. it can only be applied for variables with one conditioning variable; it provides the opportunity to support the parameterization of Bayesian Networks which would otherwise remain half-finished due to time constraints. In addition, a case study in the Murray-Darling Basin, Australia, is used to compare Bayesian Network types and software to improve the presentation clarity of large Bayesian Networks. Both case studies aimed at gaining insights on how to improve the applicability of Bayesian Networks to support environmental management.
6
A data set of monthly growing areas of 26 irrigated crops (MGAG-I) and related crop calendars (CC-I) was compiled for 402 spatial entities. The selection of the crops consisted of all major food crops including regionally important ones (wheat, rice, maize, barley, rye, millet, sorghum, soybeans, sunflower, potatoes, cassava, sugar cane, sugar beets, oil palm, rapeseed/canola, groundnuts/peanuts, pulses, citrus, date palm, grapes/vine, cocoa, coffee), major water-consuming crops (cotton), and unspecified other crops (other perennial crops, other annual crops, managed grassland). The data set refers to the time period 1998-2002 and has a spatial resolution of 5 arc minutes by 5 arc minutes which is 8 km by 8 km at the equator. This is the first time that a data set of cell-specific irrigated growing areas of irrigated crops with this spatial resolution was created. The data set is consistent to the irrigated area and water use statistics of the AQUASTAT programme of the Food and Agriculture Organization of the United Nations (FAO) (http://www.fao.org/ag/agl/aglw/aquastat/main/index.stm) and the Global Map of Irrigation Areas (GMIA) (http://www.fao.org/ag/agl/aglw/aquastat/irrigationmap/index.stm). At the cell-level it was tried to maximise consistency to the cropland extent and cropland harvested area from the Department of Geography and Earth System Science Program of the McGill University at Montreal, Quebec, Canada and the Center for Sustainability and the Global Environment (SAGE) of the University of Wisconsin at Madison, USA (http://www.geog.mcgill.ca/~nramankutty/ Datasets/Datasets.html and http://geomatics.geog.mcgill.ca/~navin/pub/Data/175crops2000/). The consistency between the grid product and the input data was quantified. MGAG-I and CC-I are fully consistent to each other on entity level. For input data other than CC-I, the consistency of MGAG-I on cell level was calculated. The consistency of MGAG-I with respect to the area equipped for irrigation (AEI) of GMIA and to the cropland extent of SAGE was characterised by the sum of the cell-specific maximum difference between the MGAG-I monthly total irrigated area and the reference area when the latter was exceeded in the grid cell. The consistency of the harvested area contained in MGAG-I with respect to SAGE harvested area was characterised by the crop-specific sum of the cell-specific difference between MGAG-I harvested area and the SAGE harvested area when the latter was exceeded in the grid cell. In all three cases, the sums are the excess areas that should not have been distributed under the assumption that the input data were correct. Globally, this cell-level excess of MGAG-I as compared to AEI is 331,304 ha or only about 0.12 % of the global AEI of 278.9 Mha found in the original grid. The respective cell-level excess of MGAG-I as compared to the SAGE cropland extent is 32.2 Mha, corresponding to about 2.2 % of the total cropland area. The respective cell-level excess of MGAG-I as compared to the SAGE harvested area is 27 % of the irrigated harvested area, or 11.5 % of the AEI. In a further step that will be published later also rainfed areas were compiled in order to form the Global data set of monthly irrigated and rainfed crop areas around the year 2000 (MIRCA2000). The data set can be used for global and continental-scale studies on food security and water use. In the future, it will be improved, e.g. with a better spatial resolution of crop calendars and an improved crop distribution algorithm. The MIRCA2000 data set, its full documentation together with future updates will be freely available through the following long-term internet site: http://www.geo.uni-frankfurt.de/ipg/ag/dl/forschung/MIRCA/index.html. The research presented here was funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) within the framework of the research project entitled "Consistent assessment of global green, blue and virtual water fluxes in the context of food production: regional stresses and worldwide teleconnections". The authors thank Navin Ramankutty and Chad Monfreda for making available the current SAGE datasets on cropland extent (Ramankutty et al., 2008) and harvested area (Monfreda et al., 2008) prior to their publication.