Modeling the Impact of Extreme River Discharge on the Nutrient Dynamics and Dissolved Oxygen in Two Adjacent Estuaries (Portugal)

Abstract

The Minho and Lima are adjacent estuaries located in the north of Portugal, with high ecological and economic importance. To address gaps in knowledge about changes in nutrient patterns in adjacent estuaries subject to different freshwater inflows, a numerical model, Delft3D, was implemented and developed, using a single domain, which allowed physical communication between estuaries. Calibration and validation of the model was successfully performed. Three numerical simulations were carried out, in which only river flows were varied (1st corresponds to a baseline numerical run, the 2nd a flood scenario, and the 3rd a drought scenario). Under flooding conditions, similar patterns were verified in both estuaries, with high fluvial discharges showing to have a reduced impact on both estuarine dynamics. In this case the nutrients were not a limiting factor for the biota, both for summer and winter seasons, since there was no significant decrease in dissolved oxygen concentration. For the drought scenario, it was observed that the estuary with the lower inflow of freshwater (Lima) was the most affected, with a significant decrease in the concentration of nutrients and oxygen dissolved in the winter season (decrease of 2 mg O2/L). In conclusion, this work reveals that it is essential to continuously monitor dam-controlled estuarine systems, as a significant decrease in river discharge will cause significant changes in the variables analysed (O2, PO4, and NO3) and may cause loss of biodiversity.

Physico-Chemical Characterization of Two Portuguese Coastal Systems: Ria de Alvor and Mira Estuary

“…Indeed, at all stations, the RMSE between predictions and observations represents less than 8% of the mean local value. Results are better than those achieved for Minho and Lima estuaries by [7].…”

“…Several estuarine systems located on the Portuguese coast have been widely studied in the past with a focus on processes inherent to different scientific areas, such as Tagus estuary [5,6], Minho and Lima estuaries [7], and Ria de Aveiro [8][9][10], among others. However, the study of the smallest has tended to occur in the estuary lower reaches [14].…”

Assessment of water quality variations due to operation of wastewater treatment plant in Ca Mau city

“…Several models have been applied in wastewater dispersion simulation, such as QUAL2K (or Q2K), DELFT 3D, and MIKE, all of which obtained favorable results in forecasting work in the early stages [1][2][3][4][5][6][7][8]. In this article, the MIKE model -software of the Danish Hydraulic Institute, has been selected to apply in the calculation of hydraulics and resources -environment, including rivers, estuaries, and coastal areas, and the sea.…”

Dynamics of Two Anadromous Species in a Dam Intersected River: Analysis of Two 100-Year Datasets

“…In the Spanish Minho basin, above the Frieira dam, there are more than 60 dams distributed over the tributaries and built mainly in the 1950s and 1960s. Despite the economic benefits and benefits of flood prevention, dams have a negative effect on biodiversity and aquatic biochemistry [34]. benefits of flood prevention, dams have a negative effect on biodiversity and aquatic biochemistry [34].…”

“…Despite the economic benefits and benefits of flood prevention, dams have a negative effect on biodiversity and aquatic biochemistry [34]. benefits of flood prevention, dams have a negative effect on biodiversity and aquatic biochemistry [34]. An important feature of the Minho River is its lower 77 km stretch that forms an international boundary between northern Portugal and the Spanish Autonomous Region of Galicia, which poses challenges to the management of aquatic resources with an economic interest, such as sea lamprey and allis shad.…”