Spatial patterns of surface water quality in the Cértima River basin, central Portugal

Abstract

The Cértima River is the principal source of water flowing into the Pateira de Fermentelos, which is one of the largest natural lakes of the Iberian Peninsula and has elevated conservation value. This study aims at a more comprehensive understanding of the spatial pattern in water quality and, thus, pollution problems in and especially upstream of the Pateira, including a comparison with a prior study in 2003. To this end, surface water samples were collected, in May 2007, at 29 sites covering the basin's four main types of water bodies, and analysed for electrical conductivity, dissolved oxygen, biochemical oxygen demand, total suspended solids, various nitrogen species, orthophosphate and chlorophyll a. The results confirmed the existence of marked pollution along the middle section of the Cértima's main course, which can be attributed to wastewater discharges of urban and animal husbandry origin in particular. This represents an important eutrophication risk to the Pateira. Current legislation and water management does not appear to tackle this risk in an entirely satisfactory manner, since the spatial patterns as well as actual values of key physic-chemical parameters do not appear to have changed markedly between 2003 and 2007. Amongst the various parameters, biochemical oxygen demand stands out for frequently exceeding the legal water quality standards. The type of water body proved helpful to explain part of the variation in some of the parameters. This includes clear differences in electrical conductivity between the right- and left-bank tributaries, illustrating well the heterogeneous and complex character of the Cértima basin.

Time-series analysis of the long-term hydrologic impacts of afforestation in the Águeda watershed of North-Central Portugal

“…A key driver was the enactment of legislation in 1938 which encouraged afforestation of areas classified as "uncultivated/wasteland", which often consisted of areas of matos (shrublands), mountain ranges, and sand dunes (Coelho et al, 1995;Estêvão, 1983;Ferreira et al, 2010;Jones et al, 2011;Silva et al, 2004). The primary species planted during this earlier period was Pinus pinaster, and beginning in the 1970s Eucalyptus globulus became the preferred species due to its faster growth and higher profitability for use in the paper pulp industry.…”

“…Across a number of catchments with winter-dominant rainfall, Brown et al (2005) found that afforestation led to much larger proportional reductions in summer flows compared to winter flows, which they attributed to the afforestation-induced changes in interception and evapotranspiration. Among these catchments, those of Gallart et al (2001) and Lewis et al (2000) demonstrated the importance of soil depth in controlling the hydrological response of Mediterranean mountain catchments in the Pyrenees and California, respectively. Other studies with somewhat similar site conditions (i.e., Bari et al, 1996;Van Lill et al, 1980) were conducted at very different temporal and spatial scales than the present study, making comparisons to their findings difficult.…”

Surface water‐groundwater exchange dynamics in buried‐valley aquifer systems

“…A unique feature of buried-valley sedimentary architecture data is the presence of gravel-dominated facies such as open-framework gravel (OFG) crossstrata, which have negligible sand content and a unimodal grain size distribution (d 50 > 2 mm). As a result, the conductivity of OFG facies can reach to up to 10 3 darcys (Ferreira et al, 2010;Jussel, 1989;Klingbeil, Kleineidam, Asprion, Aigner, & Teutsch, 1999;Lunt, Bridge, & Tye, 2004). The formation and preservation of OFG cross strata is common, especially along gravelly riverbeds (Lunt & Bridge, 2007), where they may strongly control hyporheic exchange by channelling flow wherever they intersect the channel boundary (Zhou, Ritzi, Soltanian, & Dominic, 2014).…”

What is the extension of bench terrace construction for forest plantations? The case of North Central Portugal

“…The annual rainfall varies from 1103 mm in the lower foothills of the mountain and can reach up to 2370 mm in the higher mountain zones (SNIRH, 2022). The mean temperature differs from 14°C in January to 24 in August in the lower foothills and varies from 9°C in January to 19°C in August in the higher zones (Boulet et al, 2015; Ferreira et al, 2010; Ribeiro, 2006).…”