Reduction of Uncertainties Due to Scarcity of Hydrometeorological Data for the Study of Water Availability, Apurimac Basin (Peru)

A very serious problem in the study of water availability is the scarcity of pluviometric and hydrometric data in the watersheds of interest, which limits the representativeness of these studies leading to less reliable results that will be used for the planning and design of projects of water supply, generation of energy, among others. However, in published water availability studies, the application of precipitation measured by satellite and hydrological modeling performed in basins that do not have adequate basic information to perform the calibration and validation of these models is observed. The National Meteorology and Hydrology Service (SENAMHI) shows no interest in expanding its measurement networks. The National Water Authority (ANA), the governing body and the highest normative technical authority of the National Water Resources Management System, has installed new hydrometric stations but the record length is still very short.

The objective of this research is to identify the uncertainties caused by the scarcity of basic information in the modeling of the spatial distribution of precipitation and discharges in order to solve them using complementary thematic information related to the regional analysis and the hydrological similarity with basins with information. To this goal, the Apurímac river basin located in the South-Eastern region of Peru belonging to the Atlantic catchment was selected, which has much less rainfall and hydrometric stations than the recommended number but has a few in-depth studies of climate characterization and water availability.

Here, the studied basin was characterized and compared with the Pampas and Urubamba basins using the existing thematic information and orographic effects for the regional analysis, as well as the physiographic characteristics and the status and condition of the existing rainfall and hydrometric dataset. Using the existing monthly rainfall information in the longest common period 1964 - 2015, correlation methods were used to obtain a complete and confident datasets of monthly precipitation, temperature and streamflow for this period. The influence of climate change was also analyzed. The changes of the natural streamflow due to the Angostura reservoir, located in the upper part of the basin, with a useful volume of 1 140 MCM destined to export water to the neighboring Colca basin (Pacific watershed), was included in the study. The uncertainties originated by lack of information were identified and reduced and the average annual flow calculated in the present study was compared with those obtained in previous studies, having obtained a lower value. It is recommended to promote the use of this methodology in water availability studies.