Lafayette Dantas da Luz

Developing habitat suitability criteria for water management: A case study

Abstract A method for assessing the relative quality of a wetland as habitat for fish based on hydrological factors is described. Its three major steps include: (a) simulating the hydrologic behavior based on some water management policy; (b) computing habitat suitability indexes time series derived from the values of the simulated hydrologic variables; and (c) assessing system performance based on those suitability indexes values. The method was applied to a coastal wetland of Lake Ontario in the US. Sequences of daily water levels and water temperature in the wetland were generated considering alternative watershed land use practices and Lake Ontario water level management policies. These variables were converted to habitat suitability time series for a bioindicator, the Northern Pike (Esox lucius), focusing on its early life cycles that take place in the wetland. The overall habitat suitability performance was analyzed in terms of various reliability, resilience, and vulnerability performance indices derived from those habitat suitability time series. Results show that at least for the early life cycles of the chosen bioindicator a less variable water level regime that comes mainly from Lake Ontario regulation is more beneficial than from one that results from natural variation. A more variable regime, however, seems to favour the marsh or the wetland plant habitat upon which the fish are dependent, based on an analysis not presented in this paper. In this case study the larger bordering lake had a much greater influence on wetland water levels and temperatures than did the upstream watershed. This particular study is just part of an overall evaluation of lake level management policies based on economic and social as well as ecological criteria currently underway by a joint Canadian‐United States commission. Analyses of this type based on multiple species indicators and on a broader set of environmental factors would provide a way to judge the relative ecological impacts associated with diverse lake level regulation policies.

Identification of the degree of impact of dams on the hydrologic regime of semi-arid rivers: an evaluation of the DHRAM method

The flow regulation that results from the implantation of dams causes consequences to the river ecosystems due to the modification on the characteristics of the hydrologic regime. The investigation of these changes become relevant, mainly in semi-arid regions where there is a great amount of these hydraulic structures and lack of such analyzes. Considering the above, this paper aims to evaluate the Dundee Hydrological Regime Alteration Method (DHRAM) through the classification of the degree of impact of dams located on rivers Itapicuru, Paraguacu and their tributaries, verifying the adequacy of its use to represent the semi-arid hydrologic regime. Thereby, the DHRAM was applied in three versions: considering the thresholds that define the scores to classify the degree of impact in its original set (accordingly to Black et al. (2005)); with the adjustment of those thresholds to local conditions; and, with the regrouping of variables and adjustment of thresholds. The results showed that the method in its original set is applicable to semi-arid rivers, however it tends to be very restrictive against the high natural hydrologic variability characteristic of these rivers, and it ends up pointing to a high degree of alteration for dams that are known for not causing a very siginifcant flow regulation. The DHRAM with the regrouping of variables and the adjustment of thresholds presented the classification that approached the most to the known characteristics of the studied dams, being useful for the evaluation of the impact of dams still in project, and also to guide the adoption of operating rules that minimize the most significant hydrologic alterations that are identified.

Dimensionless formulation for human stability in open flows

The stability of humans partially immersed in risky open water flows, resulting from urban flooding caused for example by dam breaks, or failures in drainage systems, or natural extreme events, is a topic of increasing interest because it involves the human safety in an environment that is more and more subjected to extreme events of hydraulic nature. The studies in this field of the applied fluid mechanics generally present equations that handle the results through dimensional quantities. These results were generally obtained in specific experiments for the evaluation of the stability of models of the human body. Intending to advance in the direction of a more general formulation, a dimensional analysis for the problem of human stability in open flows is presented here, showing dimensionless groups that represent the mentioned problem. Equations using these nondimensional groups were then developed using statistical analyses and approximations based on principles of physics and on data of the human body. The results obtained with the proposed methodology are of very good quality, presenting high correlation coefficients and good agreement between measured and calculated data.