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- Using quinine as a fluorescent tracer to estimate overland flow velocities on bare soil: Proof of concept under controlled laboratory conditionsPublication . de Lima, João L. M. P.; Zehsaz, Soheil; de Lima, M. Isabel P.; Isidoro, Jorge M. G. P.; Jorge, Romeu Gerardo; Martins, RicardoThis study presents a tracer technique based on the fluorescent properties of quinine to help on the visualization of shallow flows and allow a quantitative measurement of overland flow velocities. Laboratory experiments were conducted to compare the traditional dye tracer and thermal tracer techniques with this novel fluorescent (quinine) tracer by injecting a quinine solution and the other tracers into shallow flowing surface water. The leading-edge tracer velocities, estimated using videos of the experiments with the quinine tracer were compared with the velocities obtained by using thermograms and real imaging videos of the dye tracers. The results show that the quinine tracer can be used to estimate both overland and rill flow velocities, since measurements are similar to those resulting from using other commonly used tracers. The main advantage of using the quinine tracer is the higher visibility of the injected tracer under ultraviolet A (UVA) light for low luminosity conditions. In addition, smaller amounts of quinine tracer are needed than for dye tracers, which lead to smaller disturbances in the flow. It requires a simple experimental setup and is non-toxic to the environment.
- Estimating sheet flow velocities using quinine as a fluorescent tracer: bare, mulched, vegetated and paved surfacesPublication . Zehsaz, Soheil; de Lima, João L. M. P.; de Lima, M. Isabel P.; MGP Isidoro, Jorge; Martins, RicardoWhen direct flow velocity measurements are not feasible, the use of tracers can be a valuable tool. In the present study, both laboratory and field experiments were conducted to evaluate the applicability of quinine as a fluorescent tracer for estimating mean sheet flow velocities in different ambient light and surface morphology conditions. Quinine excels in low-light conditions when exposed to UVA light. This tracer was compared with dye and thermal tracers, all in liquid form. In these tracing techniques the tracers were injected into the flow, after which surface velocity was estimated by tracking the leading edge of the tracer plumes and applying a correction factor to calculate the mean velocity (in a water column). The visibility of the tracers was evaluated by measuring the relative luminance and contrast ratio of the quinine and dye tracer plumes. Results show that the quinine tracer can be used to estimate sheet flow velocities over a wide variety of soil and urban surfaces; it has better visibility in comparison to the dye tracer but, in some conditions, lower visibility than the thermal tracer. Although quinine is invisible under bright ambient light conditions, this tracer technique requires low-cost experimental setup and is useful in low-light conditions (e.g., night; twilight; shielded environments).
- Enhancing the spatial rainfall uniformity of pressurized nozzle simulatorsPublication . Silveira, Alexandre; MGP Isidoro, Jorge; Deus, Fábio P. de; Reis, Simone Siqueira dos; Silva, António Marciano da; Gonçalves, Flávio A.; Bretanha Junker Menezes, Paulo Henrique; Tiezzi, Rafael de O.Purpose - Rainfall simulators are used on experimental hydrology, in areas such as, e.g., urban drainage and soil erosion, with important timesaving when compared to real scale hydrological monitoring. The purpose of this paper is to contribute to increase the quality of rainfall simulation, namely, for its use with scaled physical models. Design/methodology/approach - Two pressurized rainfall simulators are considered. M1 uses three HH-W 1/4 FullJet nozzles under an operating pressure of 166.76 kPa and was tested over a 4.00 m length by 2.00 m width V-shaped surface. M2 was prepared to produce artificial rainfall over an area of 10.00m length by 10.00m width. The spatial distribution of rainfall produced from a single nozzle was characterized in order to theoretically find the best positioning for nozzles to cover the full 100m(2) area with the best possible rainfall uniformity. Findings - Experiments with M1 led to an average rainfall intensity of 76.77-82.25 mm h(-1) with a 24.88 per cent variation coefficient and a Christiansen Uniformity Coefficient (CUC) of 78.86 per cent. The best result with M2 was an average rainfall intensity of 75.12-76.83 mm h(-1) with a 21.23 per cent variation coefficient and a CUC of 83.05 per cent. Practical implications - This study contributes to increase the quality of artificial rainfall produced by pressurized rainfall simulators. Originality/value - M2 is the largest rainfall simulator known by the authors worldwide. Its use on rainfall-runoff studies (e.g. urban areas, erosion, pollutant transport) will allow for a better understanding of complex surface hydrology processes.