Confluences are locations of complex hydrodynamic conditions within river systems. The effects on hydrodynamics and mixing of temperature-induced density differences between incoming flows are investigated at a small-size, concordant bed confluence. To evaluate density effects, results of eddy-resolving simulations for a densimetric Froude number Fr = 4.9 (weak-density-effects cases) and Fr = 1.6 (strong-density-effects cases) are compared to results of simulations in which the densities of the incoming flows do not differ (no-density-effects cases). Flow patterns predicted for both weak-and strong-density-effects cases show that secondary flow develops with increasing distance from the confluence apex. The pattern of secondary flow is characterized by denser fluid on one side of the confluence moving near the bed toward the side of the downstream channel corresponding to the less dense fluid and the less dense fluid moving near the free surface in the opposite direction. This pattern of fluid motion is similar to a spatially evolving lock-exchange cross flow. In the strong-density-effects simulations, a cross-stream cell of secondary flow develops at the density interface between the flows, similar to interfacial billows generated in classical lock-exchange flows. Density effects increase global mixing with respect to corresponding no-density-effects cases regardless of whether the high-momentum stream contains the higher-density fluid or the lower-density fluid. When density effects are weak, the lock-exchange mechanism either reinforces the pattern of mixing associated with secondary flow induced by inertial forces, particularly helical motion, or opposes this pattern of mixing, depending on which tributary contains the denser fluid. When density effects are strong, flow from the upstream channel with the denser fluid moves under the flow from the upstream channel with the less dense fluid.

Ulloa et al.

No abstract

No abstract

No abstract

The emergence of the new COVID-19 virus in Peru forced the Peruvian government to take swift measures to stop its proliferation. Consequently, a state of emergency was declared, which included mandatory social isolation and quarantine. This action meant that people would transit only in emergency cases. In this context, this study’s objective is to analyze the air quality changes in terms of the capital city’s NO2 levels due to these government decisions using satellite imagery data obtained from the Sentinel-5P satellite. One critical problem is the lack of spatially distributed air quality data. The Peruvian Meteorological Service only monitors air quality in Lima, the capital city. In addition, the air quality ground stations are not always functioning. Thus, there is a need to find new reliable methods to complement the official data obtained. One method of doing so is the use of remote sensing products, although the accuracy and applicability are yet to be determined; therefore, this is the article’s focus. A temporal and spatial analysis was developed quantitatively and qualitatively to measure the levels of NO2 in eighteen regions of Lima to contrast the quarantine’s effect on polluting gas emission levels. The measurements are also compared with the official Peruvian data from ground sensors using Pearson correlation coefficients, thus, showing that Sentinel-5P data can be used for changes in the mean daily concentration of NO2. We also developed the first version of an open platform that converts the satellite data into a friendly format for visualization. The results show NO2 ambient concentration reductions compared to 2019 of between 60% and 40% in the first two weeks and between 50% and 25% in the following two weeks of the COVID-19 lockdown. However, this effect could not be observed two months after the start of the lockdown.

No abstract

Water is an essential resource for social and economic development. The availability of this resource is constantly threatened by the rapid increase in its demand. This research assesses current (2010–2016), short- (2017–2040), middle- (2041–2070), and long-term (2071–2099) levels of water security considering socio-economic and climate change scenarios using the Water Evaluation and Planning System (WEAP) in Vilcanota-Urubamba (VUB) catchment. The streamflow data of the Pisac hydrometric station were used to calibrate (1987–2006) and validate (2007–2016) the WEAP Model applied to the VUB region. The Nash Sutcliffe efficiency values were 0.60 and 0.84 for calibration and validation, respectively. Different scenarios were generated for socio-economic factors (population growth and increased irrigation efficiency) and the impact of climate change to evaluate their effect on the current water supply system. The results reveal that water availability is much higher than the current demand in the VUB for the period (2010–2016). For short-, middle- and long term, two scenarios were considered, “Scenario 1” (RCP 4.5) and “Scenario 2” (RCP 8.5). Climate change scenarios show that water availability will increase. However, this increase will not cover the future demands in all the sub-basins because water availability is not evenly distributed in all of the VUB. In both scenarios, an unmet demand was detected from 2050. For the period 2071–2099, an unmet demand of 477 hm3/year for “Scenario 1” and 446 hm3/year for “Scenario 2” were estimated. Because population and agricultural demands are the highest, the effects of reducing the growth rate and improving the irrigation structure were simulated. Therefore, two more scenarios were generated “Scenario 3” (RCP 4.5 with management) and “Scenario 4” (RCP 8.5 with management). This socio-economic management proved to be effective in reducing the unmet demand up to 50% in all sub-basins for the period 2071–2099.