Evaluación del impacto del cambio climático en los procesos hidrológicos de la Cuenca del Arroyo Feliciano, Entre Ríos, Argentina

Abstract

The Province of Entre Ríos has been affected by the intensification in the use of natural resources, without that it exist an orderly management of the same; in particular the Arroyo Feliciano watershed is one of the ones with a greater activity reconversion activity, as it changed from livestock farming to a vertiginous expansion of the agriculture, with the introduction of rice crops irrigated with superficial water and soybean, the two main crops nowadays. The Arroyo Feliciano is a course of permanent water that is born in the northeast of the department that carries his name, at a height of 75 m. asl, and it ends in the river Paraná at an approximate height of 20 m. asl. The areas drained by this course of water and his tributaries are characterised mainly by main very long and moderate slopes, with symptoms of deficient drainage. The catchment surface is 8240 km2. The mean discharge is 52.93 m3/second, (source: SSRH of the Nation) with a maximum of 2.244 m3/second, monitored during 2016. The drainage density of drainage (0.51 km/km2) is very high and results from both, the heavy textured soils and annual precipitations above the 1100 mm. Superficial and undergrounds resources until now have been utilised in a moderate way, but in shape moderate; the main uses of superficial water are in the agricultural sector, i.e. irrigation of rice crops, and watering livestock, while subterranean water is the only source of drinking water. The region has been affected by strong variations in the hydrological cycle, as well as and high spatial and temporal variability of rainfall, which generated grave problems in the agriculture and livestock sectors. This Ph. D. thesis aims to evaluate the impact of climatic change in the hydrological answers of the Arroyo Feliciano catchment, and on the infrastructure (bridges and ways) of the Province of Entre Ríos, Argentina. For this end, a description and diagnostic of the catchment has been elaborates, on the basis of existing monitoring infrastructure, soil use and hydrological network. Previous analysis of the recorded series of daily discharges shows a huge variability of its temporal distribution, with very high coefficients of dispersion and ranks of discharges (maximum – minimum = Qmax - Qmin), so that the values of mean discharges and modules, estimated by common methods, are practically a numerical abstraction. During the last years the process of agriculture intensification showed an ascending tendency, and this both, in the whole country and in the Entre Ríos province, for example production of soybean in the period 1985 to 2005 increased by 692%, while it occupied 63% of the cultivated surface in this province. Following the Intergovernmental Panel on Climatic Change (IPCC), degradation of soil and hydrological resources will be the main challenges that should be addressed by global agriculture during the next years. More recently and following climatic predictions, it has been stablished that, on average, the global increase on surface temperature will be of about 2 to 7 ºC during the period from 1900 to 2100. Also, global temperature has already increased by about 0.6 ºC from since the end of nineteen the century. The condition and quality of ways is basic importance for development of the agricultural sector; this is because production transfer to commercialisation and/ or industrialisation centres is mainly performed by vehicle transport. Taking into account available background on geological, geomorphological, climatic, hydrological, vegetable formations and soils, as well as the present land use, mathematical models have been applied to describe and simulate the present day existing hydrological response. Moreover, simulation of future scenarios, including series of maximum discharges, has been implemented, based on estimates of global climatic change; subsequently, the potential effects of this scenario on the basin infrastructure have been assessed. Hydrological simulations have been achieved using a linear semidistributed model of events, namely the so-called HEC-HMS model. This model allows studying the environmental impact of river flooding after maximum precipitations induced by climatic change, as well as the changes induced by transformation in the soil. Simulation of Climatic Change effects on the catchment called “Arroyo Feliciano” have been completed using the so-called SRES B2 scenario, which is based on assumptions emphasising local solutions, continuous increase of population (even if smaller than in A2 scenario), and intermediate levels of economic development. Finally it was concluded that, in accordance with the projections obtained using the selected model of climatic change selected, precipitation increase of about 20% are expected; in turn, this will bring about increases of peak discharges varying between 35 and 50%, which may change the recurrences period of the events obtained by application of the extreme values laws of probabilities. In addition, a statistical analysis of frequencies has been performed, which allow to verify how the increase in the expected maximum discharges could affect the flow return time obtained by statistically inference. This result leads to reconsideration designs of public civil engineering works in order to gain guarantees for safe communication in the road system and for reducing flood risks at the cities situated in dangerous zones.