Trade-off between reservoir yield and evaporation losses as a function of lake morphology in semi-arid Brazil

Abstract

This study investigates the relationships between yield and evaporation as a function of lake morphology in semi-arid Brazil. First, a new methodology was proposed to classify the morphology of 40 reservoirs in the Ceará State, with storage capacities ranging from approximately 5 to 4500 hm 3 . Then, Monte Carlo simulations were conducted to study the effect of reservoir morphology (including real and simplified conical forms) on the water storage process at different reliability levels. The reservoirs were categorized as convex (60.0%), slightly convex (27.5%) or linear (12.5%). When the conical approximation was used instead of the real lake form, a trade-off occurred between reservoir yield and evaporation losses, with different trends for the convex, slightly convex and linear reservoirs. Using the conical approximation, the water yield prediction errors reached approximately 5% of the mean annual inflow, which is negligible for large reservoirs. However, for smaller reservoirs, this error became important. Therefore, this paper presents a new procedure for correcting the yield-evaporation relationships that were obtained by assuming a conical approximation rather than the real reservoir morphology. The combination of this correction with the Regulation Triangle Diagram is useful for rapidly and objectively predicting reservoir yield and evaporation losses in semi-arid environments.

Impact of artificial destratification on water availability of reservoirs in the Brazilian semiarid

“…The effects of different conditions of air flow rates/ intermittent bubbling and uncertainties related to the meteorology/stratification patterns are estimated to affect these temperature reductions (-1°C and -2°C) in up to about ± 50%. Figure 9 shows as an example the data of precipitation and evaporation for the Trussu reservoir, which was obtained from Campos et al (2016), in addition to predictions of evaporation suppression by using Eqs. (5) and (6), considering drops of -1 and -2°C in the temperature of the epilimnion T e,i (assumed an average of 28°C).…”

“…As a consequence, serious water quality issues such as eutrophication and toxic cyanobacterial blooms have been frequently reported in stratified reservoirs, notably in semiarid areas (Bouvy et al 2000, Dantas et al 2011. Moreover, water availability in such areas is also significantly reduced (up to about 50%) by evaporation of the surface waters (Wurbs et al 2014, Campos et al 2016.…”

Modelagem simplificada do fósforo total em lagos e reservatórios brasileiros

“…Avalia-se que a eutrofização também atinja uma parcela significativa de reservatórios menores (não monitorados), os quais apresentam em geral baixas profundidades e condições precárias de proteção ambiental, sendo, portanto, mais suscetíveis ao problema. Note que, somente no Ceará, estima-se um número total de aproximadamente 30.000 reservatórios (CAMPOS et al, 2016). Logo, dada a importância desses mananciais para o abastecimento da população do Nordeste brasileiro, várias pesquisas têm sido conduzidas recentemente com o intuito de avaliar a dinâmica de fósforo em reservatórios (BEZERRA et al, 2014;VIDAL & CAPELO NETO, 2014;BAR-BOSA & CIRILO, 2015;ARAÚJO et al, 2016;PA-CHECO et al, 2016;LIMA et al, 2018).…”

Flood damping by reservoirs: proposition of a graphical parametric method

“…Only in the State of Ceará is estimated to exist about 30,000 dams (BRASIL, 2005;CAMPOS et al, 2016). Many of them were built more than 50 years ago, designed following appropriate criteria at that time and with data of that time and may constitute potential danger to life and property to downstream populations.…”