Lasst Gras darüber wachsen : Zur Überweidung der Grassteppe in der Inneren Mongolei

Die Lebensbedingungen der Nomaden in Zentralasien haben sich im letzten Jahrhundert grundlegend verändert. So wurden z.B. in der Inneren Mongolei, einer Autonomen Region im Nordosten von China, die Nomaden in der zweiten Hälfte des 20. Jahrhunderts sesshaft gemacht. In einem engen Zusammenhang mit diesen Veränderungen stehen die Überweidung der Grassteppe, Bodenerosion und Sandstürme in diesen Gebieten. Im Rahmen eines interdisziplinären Forschungsprojektes, das in Zusammenarbeit mit der Chinese Academy of Science durchgeführt und von der Deutschen Forschungsgemeinschaft gefördert wird, befasst sich eine Arbeitsgruppe des Instituts für Landschaftsökologie und Ressourcenmanagement der Universität Gießen mit Fragen zum Wasserhaushalt, mit der Wassererosion und mit dem Austrag von Kohlenstoff und Stickstoff über die Gewässer in der Inneren Mongolei

Improving irrigation efficiency will be insufficient to meet future water demand in the Nile Basin

The Nile River Basin covers an area of approximately 3.2 million km2 and is shared by 11 countries. Rapid population growth is expected in the region. The irrigation requirements of Nile riparian countries of existing (6.4 million ha) and additional planned (3.8 million ha, 2050) irrigation schemes were calculated, and the likely water savings through improved irrigation efficiency were evaluated. We applied SPARE:WATER to calculate irrigation demands on the basis of the well-known FAO56 Crop Irrigation Guidelines. Egypt (67 km3 yr-1) and Sudan (19 km3 yr-1) consume the highest share of the 84 km3 yr-1 total (2011). Assuming today’s poor irrigation infrastructure, the total consumption was predicted to increase to 123 km3 yr-1 (2050), an amount far exceeding the total annual yield of the Nile Basin. Therefore, a key challenge for water resources management in the Nile Basin is balancing the increasing irrigation water demand basin-wide with the available water supply. We found that water savings from improved irrigation technology will not be able to meet the additional needs of planned areas. Under a theoretical scenario of maximum possible efficiency, the deficit would still be 5 km3 yr-1. For more likely efficiency improvement scenarios, the deficit ranged between 23 and 29 km3 yr-1. Our results suggest that that improving irrigation efficiency may substantially contribute to decreasing water stress on the Nile system but would not completely meet the demand. Study Region: The Nile River Basin covers an area of approximately 3.2 million km2 and is shared by 11 countries. Rapid population growth is expected in the region. Study Focus: Record population growth is expected for the study region. Therefore, the irrigation requirements of Nile riparian countries of existing (6.4 million ha) and additional planned (3.8 million ha, 2050) irrigation schemes were calculated, and likely water savings through improved irrigation efficiency were evaluated. We applied a spatial decision support system (SPARE:WATER) to calculate the irrigation demands on the basis of the well-known FAO56 Crop Irrigation Guidelines. New Hydrological Insights for the Region: Egypt (67 km3yr-1) and Sudan (19 km3yr-1) consume the highest share of 84 km3yr-1 (2011). Assuming today’s poor irrigation infrastructure, the total demand were predicted to increase to 123 km3yr-1 (2050), an amount far exceeding the total annual yield of the Nile Basin. Therefore, a key challenge for water resources management in the Nile Basin is balancing the increasing irrigation water demand and available water supply. We found that water savings from improved irrigation technology will not be able to meet the additional needs of planned areas. Under a theoretical scenario of maximum possible efficiency, the deficit would still be 5 km3yr-1. For more likely efficiency improvement scenarios, the deficit ranges between 23 and 29 km3yr-1. Our results suggest that improving irrigation efficiency may substantially contribute to decreasing water stress on the Nile system but would not completely meet the demand

Upscaling von Abflussprozessen mit Multitracer-Methoden - Komplexität oder Generalisierung?

Tracerbasierte Mischungsmodelle eignen sich zur Ganglinienseparation, um hydrologische Modelle zu validieren. Bei der Anwendung in mesoskaligen Einzugsgebieten (EZG) ist von zentraler Bedeutung, ob die Informationen im Gebietsauslass das gesamte EZG repräsentieren, oder ob die hydrochemische und hydrologische Komplexität auf dieser Skala repräsentative Aussagen zu Abflussprozessen verhindert. Mithilfe tracerbasierter, multivariater, räumlicher Analysen konnte der Einfluss der hydrochemischen Heterogenität und der hydrologischen Komplexität, wie die Variabilität des Niederschlags, Skaleneffekte in Grundwasserspeichern und der Transport der unterschiedlichen Abflüsse durch das Gewässernetz, gezeigt werden. Dies macht im Kontinuum zwischen Komplexität im EZG und Einfachheit der Systemantwort am Gebietsauslass die vorgestellten diagnostischen Methoden notwendig

Discharge measurements and storm event chemistry at the San Francisco River station (Planta) in 2007-2008

To improve our knowledge of the influence of land-use on solute behaviour and export rates in neotropical montane catchments we investigated total organic carbon (TOC), Ca, Mg, Na, K, NO3 and SO4 concentrations during April 2007-May 2008 at different flow conditions and over time in six forested and pasture-dominated headwaters (0.7-76 km2) in Ecuador. NO3 and SO4 concentrations decreased during the study period, with a continual decrease in NO3 and an abrupt decrease in February 2008 for SO4. We attribute this to changing weather regimes connected to a weakening La Niña event. Stream Na concentration decreased in all catchments, and Mg and Ca concentration decreased in all but the forested catchments during storm flow. Under all land-uses TOC increased at high flows. The differences in solute behaviour during storm flow might be attributed to largely shallow subsurface and surface flow paths in pasture streams on the one hand, and a predominant origin of storm flow from the organic layer in the forested streams on the other hand. Nutrient export rates in the forested streams were comparable to the values found in literature for tropical streams. They amounted to 6-8 kg/ha/y for Ca, 7-8 kg/ha/y for K, 4-5 kg/ha/y for Mg, 11-14 kg/ha/y for Na, 19-22 kg/ha/y for NO3 (i.e. 4.3-5.0 kg/ha/y NO3-N) and 17 kg/ha/y for SO4. Our data contradict the assumption that nutrient export increases with the loss of forest cover. For NO3 we observed a positive correlation of export value and percentage forest cover