Tygodniowa prognoza zapotrzebowania na wodę w obszarach miejskich określana metodą hybrydową z wykorzystaniem transformaty falkowej-bootstrapu-sztucznej sieci neuronowej

This study developed a hybrid wavelet–bootstrapartifi cial neural network (WBANN) model for weekly (one week) urban water demand forecasting in situations with limited data availability. The proposed WBANN method is aimed at improving the accuracy and reliability of water demand forecasting. Daily maximum temperature, total precipitation and water demand data for almost three years were used in this study. It was concluded that the hybrid WBANN model was more accurate compared to the ANN, BANN and WANN methods, and can be applied successfully for operational water demand forecasting. The WBANN model simulated peak water demand very effectively. The better performance of the WBANN model indicated that wavelet analysis signifi cantly improved the model’s performance, whereas the bootstrap technique improved the reliability of forecasts by producing ensemble forecasts. The WBANN model was also found to be effective in assessing the uncertainty associated with water demand forecasts in terms of confi dence bands; this can be helpful in operational water demand forecasting.W artykule zaproponowano hybrydowy model (WBANN) wykorzystujący transformatę falkową, bootstrap i sztuczną sieć neuronową do opracowania tygodniowej prognozy zapotrzebowania na wodę w obszarach miejskich przy ograniczonej dostępności danych. Proponowany model WBANN ma na celu poprawę trafności i niezawodności prognozowania zaopatrzenia w wodę. W analizach wykorzystane zostały dobowe wartości maksymalnej temperatury, sumy opadów i zapotrzebowania na wodę z 3-letniego okresu obserwacji. Stwierdzono, że hybrydowy model WBANN jest dokładniejszy od modeli ANN, BANN i WANN i z powodzeniem może być użyty do operacyjnego prognozowania zapotrzebo zapotrzebowania na wodę. Model WBANN bardzo skutecznie prognozuje szczytowy popyt na wodę. Dobre wyniki otrzymane z modelu WBANN świadczą o tym, że zastosowana analiza falkowa znacząco poprawiła dokładność modelu, a metoda bootstrapu polepszyła niezawodność (wiarygodność) modelu poprzez prognozowanie ensemblowe. Ocena niepewności z zastosowaniem przedziału ufności wykazała dużą trafność prognoz generowanych przez model WBANN oraz jego przydatność w operacyjnym wykorzystaniu

Comparison of 2D triangular C-grid shallow water models

An ideal two-dimensional (2D) shallow water model should be able to simulate correctly various types of waves including pure gravity and inertia-gravity waves. In this paper, two different triangular C-grid methods are considered, and their dispersion of pure gravity waves, frequencies of inertia-gravity waves and geostrophic balance solutions are investigated. The proposed C-grid methods employ different spatial discretization schemes for coupling shallow water equations together with the various reconstruction techniques for tangential velocity estimation. The proposed reconstruction technique for the second method, which is analogous to a hexagonal C-grid scheme, is shown to be energy conservative and satisfies the geostrophic balance exactly while it supports the unphysical geostrophic modes for hexagonal C-grid. Because of the importance of the application of 2D shallow water models on fully unstructured grids, particular attention is also given to various types of isosceles triangles that may appear in such grids. For the gravity waves, the results of the phase speed ratio of the computed phase speeds over the analytical one are shown and compared. The non-dimensional frequencies of various modes for inertia-gravity waves are also investigated and compared in terms of being monotonic and isotropic respect to the continuous solution. The analyses demonstrate some advantages of the first method in phase speed behaviour for gravity waves and monotonicity of inertia-gravity dispersion. The results of the dispersion analysis are verified through a number of numerical tests. The first method, which is shown to have a better performance, examined through more numerical tests in presence of various source terms and results confirm its capability. 2017 Elsevier LtdThe authors acknowledge the support by NPRP grant # 4-935-2-354 .Scopu

Comparison of downscaling methods for mean and extreme precipitation in Senegal

Study region: The study considers six precipitation stations located in Senegal, West Africa. Senegal is located in the Sahel, an area that is threatened by climate variability and change. Both droughts and extreme rainfall have been an issue in recent years. Study focus: Two different statistical downscaling techniques were applied to the outputs of four regional climate models at six selected precipitation stations in Senegal. First, the delta-change method was applied to the mean annual precipitation as well as the 5, 10, 20, 50 and 100-year return period daily precipitation events. Second, a quantile–quantile transformation (QQ) was used to downscale the monthly distributions of precipitation simulated by regional climate models (RCMs). The 5, 10, 20, 50 and 100-year daily precipitation events were afterward calculated. All extreme events were calculated assuming that maximum annual daily precipitations follow the generalized extreme value (GEV) distribution. The two-sided Kolmogorov–Smirnov (KS) test was finally used to assess the performance of the quantile–quantile transformation as well as the GEV distribution fit for the annual maximum daily precipitation. New hydrological insights for the region: Results show that the two downscaling techniques generally agree on the direction of the change when applied to the outputs of same RCM, but some cases lead to very different projections of the direction and magnitude of the change. Projected changes indicate a decline in mean precipitation except for one RCM over one region in Senegal. Projected changes in extreme precipitations are not consistent across stations and return periods. The choice of the downscaling technique has more effect on the estimation of extreme daily precipitations of return period equal or greater than ten years than the choice of the climate models

Challenges and opportunities in the operationalization of the Water-Environment-Energy-Food (WE2F) Nexus: Case study of the upper Niger basin and inner Niger delta, West Africa

The ever-increasing demand for water, food, and energy is putting unsustainable pressure on natural resources worldwide, often leading to environmental degradation that, in turn, affect water, food, and energy security. The recognition of the complex interlinkages between multiple sectors has led to the creation of various holistic approaches to environmental decision making such as Integrated Natural Resources Management (INRM), Integrated Water Resources Management (IWRM), Virtual Water (VW), Water Footprint (WF) and lately the Food-EnergyEnvironment-Water nexus (WE2F). All these approaches aim to increase resource use efficiency and promote sustainability by increasing the cooperation between traditionally disjoint sectors, and mainly differ by the number and relative weights of the sectors included in their framework. They also suffer from the same face and the same barriers for implementation, some of which may never be fully overcome. The paper discusses the benefits of adopting a WE2F nexus approach in the Upper Niger Basin (UNB) and the Inner Niger Delta (IND), but also the multiple difficulties associated with its practical implementation. IWRM/WE2F initiatives in the UNB/IND such as the BAMGIRE project piloted by Wetlands International and funded by the Dutch Embassy in Mali to secure livelihoods and biodiversity in a changing environment, is taken as an example of partial success in the use of a nexus approach to watershed management. It was shown there are multiple barriers to the operational implementation of the WE2F. However, while a full understanding of all interlinkage between sectors may never be possible, data collection, scientific research and model development can improve our ability to understand the complex system in which we live, and hence take better decision