Keeping a wetland wet: hydrological studies at Aammiq

A wetland under pressure

Major spring at Aammiq

The Aammiq Wetland is the last remnant of a much larger series of lakes and marshes that once covered much of Lebanon's Bekaa Valley. As human demand for arable land and for water for irrigation has grown over the last forty years, this wetland, vital for wildlife, has come under great pressure. A Rocha Lebanon, who have been involved in managing Aammiq since 1996, have the ambitious goal of "maintaining the Aammiq Wetland at its current size, and if possible, increasing the area covered by wetland habitats."

In order to achieve that aim, studies are underway to understand the hydrology of the Aammiq area. Hydrology is the science that deals with the earth's water and it is water that allows Aammiq to exist and gives it its extraordinary value for wildlife. Without water, there would, of course, be no wetland at all but it is the behaviour of the water - how much there is, when it comes, and how long it stays - that determines the type of habitats available for all the plants and animals that use the marsh.

Yet the water issues at Aammiq are complex. The wetland gains water from the heavy winter rains but also from springs that are supplied by rain and snow melt from the heights of the adjacent Jebel Barouk mountain range. The wetland loses water by drainage to the Litani River, by evaporation and through plant transpiration during the long, hot and dry summer. Detailing and quantifying this budget of water gain and loss is far from easy. And here, as elsewhere in the world, matters are made still more complex by the human factor: the local farmers greatly affect the water balance of the wetland.

Irrigation at Aammiq: water is being pumped out of a ditch

During the wet months of the year, farmers drain water away from the area so that their fields are not flooded, while during the dry growing season they extract water from the ground and springs to irrigate their crops. Both activities alter the natural pattern of water supply to the marsh, and could reduce the ability of the marsh to support wildlife. However, farming is an important source of income to local people and cannot simply be stopped for the sake of conservation.

Big questions

There are many questions to do with water use. For instance,

How badly is the wetland affected by the pumping out of groundwater on adjacent land?
The heart of the wetland is flooded in winter; can the extent, or the duration, of that flooding be increased?
Is the wetland getting drier or wetter?
Above all, how can this precious wetland be managed in a way that balances the needs of both wildlife conservation and human need?

Surveying water levels at Aammiq by boat

To start to answer these questions, Richard Storey of A Rocha led the study of the water flow and balance in the Aammiq Wetland area. His methods included the following:

Assessing the volume of the marsh. The amount of water in the wetland was assessed by accurately mapping the area that was flooded over time using GPS (global positioning system) measurements. From this data, a series of contour maps of the volume of the marsh were produced.
Measuring rainfall and evapotranspiration. In order to calculate the water budget for Aammiq, we need to know rainfall amounts as well as temperature and wind speeds (which control water loss by evaporation or transpiration). Because there is little weather data for this part of Lebanon an ongoing program of regular measurements was started.
Measuring surface water flow. Regular measurements are being made at key points where water either enters or leaves the wetland, such as springs and ditches.
Richard Storey using a flowmeter at Aammiq

Plotting groundwater levels. Surface flow is, however, only one part of the water issue. Some idea of what goes on at shallow depth can be provided by having a series of simple measuring tubes or piezometers inserted vertically in the ground. This allows the level of the groundwater beneath the marsh soils - the water table - to be monitored. A network of such regularly monitored piezometers over Aammiq is planned which will allow the mapping of the water table over the wetland. These piezometers will also tell us how far below the ground surface the water table drops in summer, and this will allow us to answer another question: whether it is feasible to create new pools within the marsh area that remain wet all year.

Results so far

The maps and GPS maps of the receding flooded area have been completed and a measuring program in the springs and ditches is well underway. A first transect of piezometers along the length of the marsh has been installed and studies will continue into 2004. Unfortunately, heavy rains in the winter of 2002/2003 (the wettest for sixty years) have hindered some measurements. It is hoped to complete water table measurements during the dry period in 2003.

Already results have shown that the obvious springs at the western end of the marsh represent only 50-67% of the total inflow to the wetland. This means that unmeasured sources, almost certainly springs that emerge near the middle of the marsh area, supply a much greater amount of water than previously thought.

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For further information on this project, contact lebanon@arocha.org