Vertical hydraulic gradient research in hyporheic zone of Beberibe river in Pernambuco State (Brazil)

Abstract

The interaction between groundwater and surface water occurs naturally and is dependent on the dynamics in the hyporheic zone. The hyporheic zone is the interface between the surface water source and the phreatic aquifer and it's a system that also influences the water quality. An important feature is the ability to flux in this zone. This work aimed to evaluate the vertical hydraulic gradient in the hyporheic zone at two points in Beberibe river, Olinda-PE, to understand the hyporheic environment characteristics and water flow dynamics in experimental area, in addition to identify the existence of hydraulic connection between surface water and groundwater. The experimental phase consisted of infiltration tests in riverbed with cylinder infiltrometer and vertical hydraulic gradients readings with differential piezometer, complemented with grain size information, for an assessment of the water budget between the river and the aquifer. Analyzing the behavior of the interaction over the period of 10 months, it was observed that the Beberibe river (middle course) contributes to the groundwater recharge in most of the time. The average infiltration rate was 1.02 mm/min in point 1 and 0.85 mm/min in point 2. It was concluded that there is a variability in flow direction, which often is top-down, but may undergo change in the stream showing upstream after long periods of rainfall. Another conclusion is that grain size distribution of bed sediment, that is predominantly sandy, influences hydraulic conductivity of hyporheic zone and influences consequently the vertical flow rates.Keywords: River-aquifer interaction; Infiltration; Cylinder infiltrometer; Differential piezometer; Hyporheic zone. RESUMOA interação entre águas subterrânea e superficial ocorre naturalmente e depende da dinâmica na zona hiporreica. A zona hiporreica é a interface entre o corpo hídrico superficial e o meio subterrâneo, sendo um sistema que também influencia a qualidade da água. Uma importante característica é a capacidade de fluxo nesta zona. O trabalho objetivou avaliar o fluxo vertical de água na zona hiporreica em dois pontos do rio Beberibe, Olinda -PE, para compreender as características do ambiente hiporreico e a dinâmica do fluxo de água nesta zona, além de identificar a existência de conexão hidráulica entre a água superficial e subterrânea. A fase experimental consistiu em ensaios de infiltração no leito com infiltrômetro de cilindro e leituras da diferença da carga hidráulica com piezômetro diferencial, complementadas com informações granulométricas, para uma avaliação da capacidade de transporte de volumes hídricos entre o rio e o aquífero. Analisando-se o comportamento da interação ao longo do período de 10 meses, verificou-se que o rio Beberibe no seu curso médio contribui para a recarga do lençol freático em boa parte do tempo, sendo a média da taxa de infiltração de 1,02 mm/min no ponto 1 e de 0,85 mm/min no ponto 2. Concluiu-se que há uma variabilidade no sentido do fluxo, que geralmente é de cima para baixo, mas pode so...

Interação rio-aquífero e a meiofauna do ambiente hiporreico

“…Através da aplicação de um modelo computacional, Paiva et al (2013), observaram que na área de estudo o rio Beberibe contribui para o aquífero, onde no período úmido a contribuição é o dobro em relação ao período seco. Através de ensaios de infiltração na zona hiporreica, Veras et al (2016) forneceram informações sobre a troca hídrica que ocorre entre o rio e o aquífero num trecho do rio Beberibe, onde comprovou-se que em alguns pontos o rio contribui para o abastecimento do aquífero através do fluxo vertical descendente.…”

Evidence of protective effects on aquifer recharge from polluted tropical rivers: An analysis of hyporheic meiofauna and sediments

“…In addition, the effect of the river hydrodynamics influences vertical distribution, since benthic organisms tend to protect themselves during more intense flow events (Giere, 2009). During the winter and after rainfall events, it is more likely to observe downward vertical flow conditions and higher flow rates in the Beberibe River, as verified by Veras, Cabral, Paiva, and Barcellos (2016). For this reason, the 4-6 cm layer had a greater abundance than the surface layer in July at P2 and P3 and in April at P1.…”

Zebrafish as a biological model for assessing water quality along tropical hydrographic river basins in Northeast Brazil

“…Sites F1 and F2 are in the upper and middle reaches of the Beberibe River, which are inserted in remnants of the Atlantic Forest, which allowed these sites to have good water quality. Sites F3, F4 and F5 are located in an area of dense urbanization and receive a signi cant load of domestic sewage, which results in a considerable increase in the level of pollution in this river (Veras et al, 2016;Veras et al, 2019), aggravated by the direct disposal of waste from small industries in its surroundings. Previous studies have detected the presence of intestinal parasites (mainly protozoa and helminths) (Freitas et al, 2015) and pharmaceutical products (diclofenac and paracetamol) (Veras et al, 2019) in water samples from the Beberibe River, indicating it is the direct destination of untreated domestic waste in the river.…”