Presentation from Tunisia - Mr NASRALLAH


General presentation of the hydrological service

GENERAL SUPERVISION OF WATER RESOURCES

1 Mr Nasrallah works in the measurement network division. This division controls 870 rain gauges (daily rainfall), 100  automatic recording rain gauge and 100 hydrometrical stations.

2 The department of files and water year books is in charge of elaborating the data, updating the files and publishing hydrological and rainfall water year books.

3 The department of hydrological studies and research leads studies on request, publishes monographies or reports on representative watersheds.

Tunisia has not enough water, the rainfall distribution is not regular, this country knows complete years without rainfall. The majority of the territory faces a semi-arid climate. The yearly rainfall varies from 1,500 to less than 200 mm.
For all these reasons, hydrologists in Tunisia are obliged to count every drop of water that falls in the country. To manage the rare water, they have had to build dams and lead a severe politic of management of water.

Tunisia began to modernize the network, they did it carefully and step by step because the market of this type of equipment is not stable and the technologies change every year or even more often.
With this in mind, Tunisia installed 10 automatic stations equipped with radio transmission, 10 stations equipped with Argos satellite transmission and about 10 stations of automatic acquisition.

They met some problems with the radio transmission, the management is complicated. Argos transmission does not provide a transmission in near real time, it is operating correctly for slow rising flood wadis, but inappropriate for rapid rising flood wadis (the records are not correct for the peak of the floods).

14 territory zones are managed by regional offices. Every regional office collects the data, maintains the stations in its area. They send the data to central section in Tunis on diskettes or on paper when their means are not adequate.

Selection of station for the MED-HYCOS project

For the Med-Hycos project, Tunisia chose 5 stations. 3 in the north of the country. In the central region the fifth station causes some problems to be justified in the project because rains are scarce but when they occur, they are very important. It is thus representative of the spatial distribution of rain in North Africa and for this could be justified.