• UNESCO.org/
• Natural Sciences/
• Freshwater/
• IHP/
• Land-habitat hydrology/

• Themes
• Global changes and water resources
• Integrated watershed and aquifer dynamics
• Land-habitat hydrology
• Water and society
• Water education and training
•  

• Worldwide
• 
  
• Africa
• Arab States
• Asia and the Pacific
• Europe and North America
• Latin America and the Caribbean
•  

Land-habitat hydrology

Focal areas

• Drylands
• Wetlands
• Mountains
• Small islands and coastal zones
• Urban areas and rural settlements

Landform, land use and climate determine the habitats of humans, flora and fauna. How does the physical environment interact with the ecological one? How is water affected by climate and geography? How do fragile ecosystems affect water management?

The aims of this theme

The general aims of IHP activities implemented in the framework of the theme 'Land-habitat hydrology' are:

• to develop integrated approaches to the study of hydrologic systems as major constituents of environmental systems influenced by different climatic, geographic and human activities through interdisciplinary research that aims to identify and model the interactions of the flow paths of water, sediments, nutrients and pollutants
• to strengthen understanding on a regional level for IWRM through the analysis of societal interactions
• to enhance modelling capabilities for the physical processes of the water cycle at the regional and mesoscale, within seasonal to decadal timeframe
• to develop methodologies for the proper management of urban water under different climatic conditions
• to assess the impact of global change in the different climatic zones and landforms and to propose mitigation schemes to reduce the effects of extreme weather events in the respective zones
• to strengthen research networks on water in different climatic zones
• to enhance the understanding of specific hydrologic processes characterizing certain climatic zones and landforms, particularly the recharge mechanism, evaporation and evapotranspiration and their interactions with water quality
• to institute proper water resource assessment methodologies matching environmental and socio-economic features of climatic regions
• to coordinate the hydrologic activities and develop relevant tools for water resources analyses and management at the regional level
• to further develop ecohydrology as an interdisciplinary approach at the landform/land use scale
• to improve knowledge on the functioning of terrestrial and aquatic environmental systems with respect to water as a primary habitat, storage and transportation media
• to help conserve habitats to maintain aquatic communities and biodiversity.

Different climates, different water challenges

Arid and semi-arid zones

Arid and semi-arid zones are normally under higher water stress than other regions and have experienced high population growth, as have the humid tropics, commonly resulting in serious water problems. In fact, over 90% of the world’s developing countries are located within these two climatic areas. The most common source of water supply in arid and semi-arid areas is groundwater (surface water tending to be limited in space and time). The situation is likely to grow much worse in the coming years and could reach a possible conflict stage, especially in the cases of shared water resources. There is, therefore, a need to develop projects that will help reduce the water problems experienced in these regions.

Humid tropics

The humid tropics region plays a major role in the global hydrological cycle (this region is home to over 1.2 billion hectares of tropical rain forest and a substantial part of the world’s estimated 30 million species of plants and animals). Managing the water resources in the humid tropics should be promoted so as to meet society’s needs while at the same time protecting the natural resources, giving due consideration to both supply and demand. But proper water management can only be established on the basis of a clear understanding of the scientific principles that govern water-related processes.

Temperate zones

Temperate zones, while normally associated with less dramatic hydrologic phenomena than those of the arid or humid tropical zones, remain in the focus of interest of the Programme: intensive land use, industrialization, infrastructure development, etc., give the temperate zones high priority for studies of the interactions of climate and anthropogenic influences and their joint impact on the hydrological cycle. They too will be affected by climate change. Furthermore, having the most extensive long-term observation records and networks, temperate zone catchments can serve as excellent bases for research aiming to quantify impact-induced changes on the hydrologic regime.

Cold zones

Cold zones include high-latitude and high-altitude areas in which snow, ice and permafrost reign. Cold zones cover wide areas and influence global climate and global water/energy circulation to a large extent; they play significant roles in global and regional hydrology and are potential sources of water. The role of avalanches, ice-jam floods and other events is only now beginning to be understood in terms of not only damage but also of replenishment of important northern habitats and their ecosystems. Moreover, cold regions are among those likely to be most affected by climate change. Although there has been considerable scientific progress in prediction capabilities, there remain significant gaps that prevent the application of physics-based modelling, and thus necessitate resorting to empiricism. While that approach can be of some utility where site-specific processes and stationary climatic conditions exist, it is inherently unreliable under those conditions that would prevail during a period of changing climate.

The specific challenge of fragile ecosystems

Apart from those general climatic regional classifications, one needs to consider specific hydrologic and water resources management problems of the fragile ecosystems of drylands, wetlands, mountains, coastal zones and small islands, irrespective of their geographic/climatic locations.

Drylands

Drylands are associated with deserts and semi-deserts; however, in the sense of water interactions drylands can be considered all those areas which do not provide adequate quantity and year-round distribution of precipitation to sustain a society’s activities without additional water resources management activities (e.g., importation and water harvesting). Drylands can therefore be found in any climatic zone.

Wetlands

Wetlands are identified as particular areas of concern, because they play an essential ecological role in a predominantly water-determined environment. Wetlands are increasingly endangered by both pollution and land reclamation. Water interactions are not well understood in wetlands, and additional efforts are needed both for preservation and rehabilitation purposes.

Urban, peri-urban and rural settlement areas

Also important are urban, peri-urban and rural settlement areas. Urban environments have emerged as the predominant living space of humanity, with the inherent social, ecological and water management challenges, such as:

• erosion and sedimentation
• floods induced by encroaching urbanization
• freshwater and salt water intrusion both into the surface water and groundwater environments
• appropriate water resources management strategies specific to small islands.

The interference by rapidly developing urban developments along coastal zones, on islands and/or in mountainous areas further influence the magnitudes of the problems to be tackled.