In 1994 Jasminko Karanjac spent one month in Santo Domingo as a consultant hydrogeologist to the German Technical Assistance (GTZ). The ground water system of Valle de Constanza has been used in that mission as an example of (1) modern computerized processing and management of ground water data, and (2) mathematical modeling of the system flow regime and its reaction to recharge and discharge.
Valle de Constanza is located in the central part of the Dominican Republic. The valley of Constanza is a sedimentary basin located 100 km NW of the capital of Dominican Republic. It has an extension of 7 km E-W and 4 km N-S and an altitude around 1,200 m. The valley is well known for its vegetables and a very intensive irrigation is needed during 2/3 of the year.
The model concluded that the ground water system of Valle de Constanza was used up to its maximum in its northern part. The pumping in that area has already reached about 3 million cubic meters (MCM). A portion of the aquifer in that part is already drying up during extended dry spells. The southern part of the valley is not yet exploited to its potential.
The model concluded that the sustained yield of the Constanza alluvial aquifer is between 6 and 7 MCM/year. The lower value is correct for a conservative estimate of the return irrigation of about 20%. The upper value is more in line with very high estimate of the percentage of irrigation supplied water that returns and recharges the aquifer.
The United Nations Ground Water for Windows (GWW) software was used to establish a basic documentation ("Documentacion Basica") storage system for all data relevant to the Valle de Constanza project.
The staff of INDRHI (Instituto Nacional de Recursos Hidraulicos) was trained by the consultant in using the GWW software and in preparing input data for a model. The United Nations modeling software (UN/GWMOD), authored by J. Karanjac, was used in this exercise.