A digital global map of artificially drained agricultural areas : documentation

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.Landwirtschaftliche Drainagen, z.B. durch Gräben oder unterirdische Dränrohre, werden angewandt um hohe Grundwasserstände zu kontrollieren und damit einhergehende Vernässung und Versalzung des Bodens zu vermeiden. Neben anderen Faktoren beeinflussen Drainagen die Nährstoffbilanz durch Erhöhung der Stickstoffauswaschung sowie Veringerung von Denitrifikation. Um den terrestrischen Stickstofftransport simulieren zu können, wurde ein globaler Datensatz der landwirtschaftlichen Dränageflächen in einer Auflösung von 5' x 5' erstellt. Die Karte zeigt den Anteil der Zellflächen mit künstlicher Drainage. Daten zu Drainageflächen in Ländern sowie subnationalen Einheiten wurden mit globalen Datensätzen zur Verteilung der landwirtschaftlichen Flächen (Ramankutty et al., 1998) sowie zur Verteilung bewässerter Flächen (Siebert et al., 2005) kombiniert. Für 11 Länder konnten subnationale Statistiken zur Dränagefläche verwendet werden. Karten mit Umrissen der Dränageflächen standen für sechs Länder zur Verfügung. Insgesamt wurden global 167 Mio ha Fläche als landwirtschaftliche Dränageflächen ausgewiesen. Auf Grund der geringen Auflösung der Eingangsdaten wird die Verwendung des Datensatzes nur für globale oder kontinentale Studien empfohlen. Dieser Bericht beschreibt den Datensatz selbst, die Methodik zur Erzeugung des Datensatzes sowie die Informationsquellen und diskutiert die Unsicherheit

To restore or not? A valuation of social and ecological functions of the Marais des Baux wetland in Southern France

The Marais des Baux wetland in southern France has for centuries been subject to drainage, almost causing its entire disappearance. With an increasing awareness of wetland ecosystem services, the extensive drainage is being questioned today. To guide policy-makers and landowners in their decision-making, we use a Choice Experiment to elicit the preferences of the general public for potential land use and activity changes in the Marais des Baux. These changes concern wetland restoration, the extent of tree hedges, recreational opportunities, mosquito control and biodiversity.

L’impact du drainage agricole souterrain sur la morphologie des petits cours d’eau dans la région de Cookshire, Québec

Le drainage agricole souterrain a des effets sur l'hydrologie des bassins versants, ce qui, selon toute vraisemblance, se répercute sur la morphologie des cours d'eau. Cette note montre que, pour une même superficie de drainage, les petits cours d'eau des bassins versants où il y a drainage souterrain sont plus larges et de plus grande dimension que ceux sans drainage souterrain. Bien que le lien entre cet effet et les changements du régime hydrologique n'ait pu être établi directement, les résultats laissent croire à une augmentation des débits de pointe par suite de l'implantation des drains souterrains.Land drainage induces hydrological changes which should effect stream channel morphology. This paper shows that, for a similar drainage area, small stream channels of watersheds with land drainage are larger in width and size than those without land drainage. Despite the fact that a direct link between this morphological effect and changes in the hydrological regime has not been established, these results suggest an increase in peak discharge following the introduction of land drainage

2004 Coastal Illicit Connection Identification and Elimination Grant Project

The New Hampshire Department of Environmental Services (DES) received funds in 2004 from the New Hampshire Estuaries Project (NHEP) to administer grants to coastal municipalities to eliminate illicit discharges into their storm drainage systems. This final report describes the two projects that were funded under this grant. Projects in Dover, and Portsmouth involved eliminating sewage discharges into storm drainage systems from houses, apartment buildings, and commercial buildings. All of these efforts helped improve water quality in the coastal area by reducing pollution. NHEP chose to fund illicit discharge detection and elimination projects for a number of reasons. Primarily, this grant was established in order to fulfill several water quality action plans identified in the NHEP Management Plan. In addition, the Coastal/Piscataqua watershed has been identified by DES as a priority watershed in need of restoration. DES has worked in the coastal watershed since 1996 to reduce bacteria inputs that cause the closure of shellfish beds. Finally, the communities that were awarded grants are regulated as small municipal separate storm sewer systems (MS4s) under the Phase II federal stormwater regulation. The financial assistance these municipalities received has helped them comply with one of the requirements of these regulations

2001 Storm Drain Monitoring and Municipal Training Project

This final report describes the training sessions held for municipal officials in the Seacoast on the topic of investigating and locating illicit discharges into the storm drainage system. A Memorandum of Agreement (MOA) between NHEP and DES established funding for this project. DES held two, half-day training sessions in January 2003, one in Dover and one in Epping. Each training session offered four presentations from DES staff. NHEP funding paid for the printing costs of an illicit discharge detection and elimination manual, handout materials, compact discs containing all of DES’s illicit discharge monitoring data in the coastal watershed, and food for the training sessions

2005 Coastal Illicit Connection Identification and Elimination Grant Project

The New Hampshire Department of Environmental Services (DES) received funds in 2005 from the New Hampshire Estuaries Project (NHEP) to administer grants to coastal municipalities to eliminate illicit discharges into their storm drainage systems. This final report describes the projects that were funded under this grant. Projects in Rye and Somersworth involved eliminating sewage discharges into storm drainage systems from houses. A project in Portsmouth involved developing a standard operating procedure manual and recommendations for future training for illicit discharge detection and elimination (IDDE). The removal of illicit discharges in Rye and Somersworth helped improve water quality in the coastal area by reducing pollution. NHEP chose to fund IDDE projects for a number of reasons. Primarily, this grant was established in order to fulfill several water quality action plans identified in the NHEP Management Plan. In addition, the Coastal/Piscataqua watershed has been identified by DES as a priority watershed in need of restoration. DES has worked in the coastal watershed since 1996 to reduce bacteria inputs that cause the closure of shellfish beds. Finally, the communities that were awarded grants are regulated as small municipal separate storm sewer systems (MS4s) under the Phase II federal stormwater regulation. The financial assistance these municipalities received has helped them comply with one of the requirements of these regulations

The Varied Character of the Des Moines River Valley in Central Iowa

The drainage system on the Des Moines River is quite varied between Humboldt and Des Moines. The variation in drainage characters is highlighted on a map prepared from aerial photographs and topographic sheets. The northern part of this area is associated with the Mankato drift sheet and is characterized by poorly developed, non-integrated drainage. The central part of the drainage system in Boone County flows across the Cary ground moraine. In this area the tributaries are short, intermittent, and deep, and appear as gullies and washes. Just south of Des Moines, the drainage makes another sharp change, and in this area is associated with the Kansan drift. It is well integrated and featured by a relatively small number of far-reaching primary tributaries. It seems to be more than coincidental that the change in character of the drainage is so closely associated with the relative ages of the drift sheets comprising the drift plain

Land Drainage Technology - Canada's Leadership Role

Land drainage technology remained static from the days of the Pharaohs to 1900. Practical drain installation machinery was introduced just prior to 1900 and was gradually improved to the 1960s. From 1850, clay drain tile were manufactured in hundreds of small rural plants in Ontario. These tile were installed by hand or by open trench machinery. In the late 1960s land drainage technology advanced rapidly with the introduction of plow-in equipment and the parallel development of corrugated plastic drainage tubing. Laser technology was introduced to make the operation efficient. The design, construction, and world-wide sale of this new equipment began in Ontario and has developed major side industries such as the production of tubing for veins and arteries of humans. The paper discusses the development of the technology using four time periods.Cet article retrace les quatre grandes périodes de développement de la technologie du drainage des terres, restée statique de l’époque des Pharaons jusqu’à 1900. Des machines facilitant la pose des drains ont fait leur apparition au tournant de 1900 et ont été perfectionnées graduellement jusqu’en 1960. Au milieu du 19e siècle, des drains formés de tuiles d’argile étaient produits dans des centaines de petites manufactures rurales en Ontario. Les tuiles étaient installées à la main ou à l’aide de machines servant à creuser des tranchées. A la fin des années 1960, la technologie du drainage avança rapidement grâce à l’utilisation des techniques de labourage et au développement de tuyaux de plastique ondulé. L’utilisation de lasers a rendu les équipements de drainage plus efficaces. En Ontario, la conception, la construction et la vente de ces équipements à l’échelle mondiale a donné naissance à des industries de pointe comme celles spécialisées dans la production de tuyaux utilisés dans les veines et artères humaines

Drainage Needs and Returns in North-Central Iowa

Current status of drainage and estimated drainage needs of the soils in the Des Moines River basin as indicated from an extensive survey are presented. A high percentage of the area has the potential for receiving benefits by improving county mains and on-the-farm drainage. Analyses have been made of the economic potential for drainage improvements by comparing three drainage input levels. Benefit-cost ratios indicate drainage of very poorly drained and poorly drained soils is a good investment for corn and soybean production

Simulating surface water and groundwater flow dynamics in tile-drained catchments

Pratique agricole répandue dans les champs sujets à l’accumulation d’eau en surface, le drainage souterrain améliore la productivité des cultures et réduit les risques de stagnation d’eau. La contribution significative du drainage sur les bilans d’eau à l’échelle de bassins versants, et sur les problèmes de contamination dus à l’épandage d’engrais et de fertilisant, a régulièrement été soulignée. Les écoulements d’eau souterraine associés au drainage étant souvent inconnus, leur représentation par modélisation numérique reste un défi majeur. Avant de considérer le transport d’espèces chimiques ou de sédiments, il est essentiel de simuler correctement les écoulements d’eau souterraine en milieu drainé. Dans cette perspective, le modèle HydroGeoSphere a été appliqué à deux bassins versants agricoles drainés du Danemark. Un modèle de référence a été développé à l’échelle d’une parcelle dans le bassin versant de Lillebæk pour tester une série de concepts de drainage dans une zone drainée de 3.5 ha. Le but était de définir une méthode de modélisation adaptée aux réseaux de drainage complexes à grande échelle. Les simulations ont indiqué qu’une simplification du réseau de drainage ou que l’utilisation d’un milieu équivalent sont donc des options appropriées pour éviter les maillages hautement discrétisés. Le calage des modèles reste cependant nécessaire. Afin de simuler les variations saisonnières des écoulements de drainage, un modèle a ensuite été créé à l’échelle du bassin versant de Fensholt, couvrant 6 km2 et comprenant deux réseaux de drainage complexes. Ces derniers ont été simplifiés en gardant les drains collecteurs principaux, comme suggéré par l’étude de Lillebæk. Un calage du modèle par rapport aux débits de drainage a été réalisé : les dynamiques d’écoulement ont été correctement simulées, avec une faible erreur de volumes cumulatifs drainés par rapport aux observations. Le cas de Fensholt a permis de valider les conclusions des tests de Lillebæk, ces résultats ouvrant des perspectives de modélisation du drainage lié à des questions de transport.Tile drainage is a common agricultural management practice in plots prone to ponding issues. Drainage enhances crop productivity and reduces waterlogging risks. Studies over the last few decades have highlighted the significant contribution of subsurface drainage to catchments water balance and contamination issues related to manure or fertilizer application at the soil surface. Groundwater flow patterns associated with drainage are often unknown and their representation in numerical models, although powerful analysis tools, is still a major challenge. Before considering chemical species or sediment transport, an accurate water flow simulation is essential. The integrated fully-coupled hydrological HydroGeoSphere code was applied to two highly tile-drained agricultural catchments of Denmark (Lillebæk and Fensholt) in the present work. A first model was developed at the field scale from the Lillebæk catchment. A reference model was set and various drainage concepts and boundary conditions were tested in a 3.5 ha tile-drained area to find a suitable option in terms of model performance and computing time for larger scale modeling of complex drainage networks. Simulations suggested that a simplification of the geometry of the drainage network or using an equivalent-medium layer are suitable options for avoiding highly discretized meshes, but further model calibration is required. A catchment scale model was subsequently built in Fensholt, covering 6 km2 and including two complex drainage networks. The aim was to perform a year-round simulation accounting for variations in seasonal drainage flow. Both networks were simplified with the main collecting drains kept in the model, as suggested by the Lillebæk study. Calibration against hourly measured drainage discharge data was performed resulting in a good model performance. Drainage flow and flow dynamics were accurately simulated, with low cumulative error in drainage volume. The Fensholt case validated the Lillebæk test conclusions, allowing for further drainage modeling linked with transport issues