Ecuador: Hydrologic forecast system for the foothills of Pichincha volcano (SISHILAD)

Ecuador's capital, Quito (2,850 meters above sea level), lies at the foot of Pichincha volcano (4,650 meters above sea level). It is crisscrossed by numerous seasonal streams that descend from the mountain and are characterized by their sudden surges and high sediment content. This causes frequent flooding in the city, which is also affected by landslides and mudslides that originate in the foothills of the volcano.

In order to study and minimize these problems, the Municipal Water and Sewerage Authority of Quito (EMAAP), The National Meteorology and Hydrology Institute of Ecuador (INAMHI) and the Institut Français de Recherche Scientifique pour le Développement en Cooperation (ORSTOM) have launched the SISHILAD Project, aimed at identifying the risks posed by these events and establish an effective operational forecasting and early warning system for events connected with extreme precipitation.

These goals were set because Quito is in a very heterogeneous mountainous setting, and adopting indiscriminately monitoring and forecasting methodologies developed for other physical and geographical contexts would simply not work. Therefore, experimental hydro-meteorological, edaphic and geotechnical research is currently in progress on the slopes of Pichincha volcano. -Modern physical and mathematical modeling procedures are being used, as well as geographic information systems (GIS) combined with numeric geomorphic models. All this will increase the reliability of forecasts, since they will be based on real data.

A hydro-meteorological network - made up of nine pluviographs and five limnigraphs - has been in operation for a year in two experimental basins. The data gathered will allow scientists to calibrate and validate a distributed-parameters hydrologic model that will help to assess the volume and flows of water into the basins which enter the sewage system. Studies are also underway on the geospatial variability of rainfall, which is essential in order to define the risks posed by downpours and the impact of floods. Edaphologic research has focused on physical onsite simulation of rainfall in order to learn about the hydrodynamics of the soil (hydraulic conductivity, runoff coefficients, etc.), as well as the types of erosion and soil loss and the influence of vegetation on the magnitude of superficial runoff. These tasks involve a detailed mapping of soils (including their physical, chemical and mineralogical characteristics), the establishment of experimental lots of various dimensions, and aerial photography monitoring of erosion.

By the time the project is completed in 1998, a hydrologic forecasting and landslide monitoring system will be in place that will reduce the risks to the city. The system is expected to operate in real time and provide reliable environmental data.

For more information, contact:

Dr. Edgar Ayabaca, EMAAP-Quito, Proyecto SISHILAD
Apdo. 1370, Quito, Ecuador. FAX.: (593-2) 446-326.
E-mail: janeau@orstom.ecx.ec