Rainfall-runoff modeling in ungauged basins continues to be a great hydrological research challenge. A novel approach is the Long-Short-Term-Memory neural network (LSTM) from the Deep Learning toolbox, which few works have addressed its use for rainfall-runoff regionalization. This work aims to discuss the application of LSTM as a regional method against traditional neural network (FFNN) and conceptual models in a practical framework with adverse conditions: reduced data availability, shallow soil catchments with semiarid climate, and monthly time step. For this, the watersheds chosen were located on State of Ceará, Northeast Brazil. For streamflow regionalization, both LSTM and FFNN were better than the hydrological model used as benchmark, however, the FFNN were quite superior. The neural network methods also showed the ability to aggregate process understanding from different watersheds as the performance of the neural networks trained with the regionalization data were better with the neural networks trained for single catchments.
Inter-basin water transfers are the root of many conflicts, and water scarcity accentuates them. Those conflicts involve the priority of water use between regions. The Jaguaribe Metropolitan system, located in the Brazilian semiarid region, presents conflicts amongst different water users: irrigated perimeters, industry, and households. This paper analyzed the Jaguaribe Metropolitan water transfer during the 2012–2018 drought by considering environmental and societal aspects. Changes in consumption and users’ drought perception were assessed. The results showed that the drought was longer and more severe in the region that provided water (i.e., Jaguaribe) than in the region that received it (i.e., FMR). Jaguaribe irrigators were aware of the beginning of the drought, but it did not result in immediate consumption control. On the other hand, drought perception was delayed in the FMR. The results of this study suggested that the water allocation decision-making process should include not only the water demands but also the characteristics of the drought and how people perceive it. The main strategy for improving water governance seems to be promoting integrated regional planning and the empowerment of participatory management.
Droughts affect basic human activities, and food and industry production. An adequate drought forecasting is crucial to guarantee the survival of population and promote societal development. The Standard Precipitation Index (SPI) is recommended by the World Meteorological Organization (WMO) to monitor meteorological drought. Using drought classification based on SPI to build Markov chains is a common tool for drought forecasting. However, Markov chains building process produce uncertainties inherent to the transition probabilities estimation. These uncertainties are often ignored by practitioners. In this study the statistical uncertainties of using Markov chains for drought annual forecasting are assessed. As a case study, the dry region of the State of Ceará (Northeastern Brazil) is analyzed, considering the precipitation records from 1911 to 2019. In addition to 100-year database for Markov chain modeling and 8-year data (2012-2019) for forecasting validation, four fictional database extensions were considered in order to assess the effect of database size in the uncertainty. A likelihood ratio is used to assess model performance. The uncertainties assessment showed that an apparent performant Markov chain model for drought class forecasting may not be more informative than the historic proportion of drought class. Considering these uncertainties is crucial for an adequate forecasting with Markov chains.
<p>Small communities of the semi-arid region suffer not only with water scarcity but also with data scarcity. The lack of data to perform water management at the local level is a common problem faced in developing countries. The absence of monitoring of water levels of small reservoirs across Cear&#225; State (Northeast Brazil) results in inefficiencies in local water management and in difficulties to fully comprehend the extension of the impact of these changes in the natural streamflow and in the water supply for the state&#8217;s network of strategic dams. Small reservoirs construction is the individual private strategy mostly performed to cope with the local droughts. Recent studies shows a strong expansion of this strategy in the recent years, with the construction of more than 100.000 small reservoirs just in one of the state basins. This aspect reveals the necessity of strategies to obtain reliable information about these small reservoirs to perform a comprehensive estimation of these reservoirs impacts in both the local and state level of water management. In this study, local drone images were obtained for a small reservoir in the Cear&#225; State. Remote sensing was used to obtain the reservoir depth-area-volume relationship and reverse water balance technique was used to estimate the different water fluxes and assess the local water availability. The results shows the inefficiency of these small reservoirs due to high evaporation losses, reflecting its high vulnerability to droughts. The proposed methodological scheme proves to be powerful in generating hydrological information by the intricate use of data, besides being replicable for other reservoirs in arid and semiarid regions.</p>
<p>Climate change has modified global and local water cycle patterns inducing more intense and severe drought events. In the Cear&#225; state (Northeast Brazil), a semiarid region very vulnerable to droughts, groundwater acts as a strategic reserve to ensure water security for small rural communities. Well drilling jointly with the building of dams and cisterns are the main policy performed by the public authority to cope with the droughts. This study performed a preliminary qualitative analysis to investigate the anthropogenic effect of the recent drought (2012-2016) in the local hydrogeological environment. The study area selected was the micro-basins of the Algod&#227;o and Forquilha creek, in which the alluvial aquifer has been monitored by Funceme since 2010. This aquifer has a great importance for local agricultural development and the water supply for domestic activities. A historical analysis of the evolution of well drilling was performed. In the physical context, the piezometric level of the wells monitored were evaluated. The well drilling was notably more intense between the years 2015 and 2018 and a continuous drawdown of the groundwater level was observed in response to the last drought event. Since 2017 the piezometric level started to rise, however, the monitoring reveals a different pattern of the piezometric levels after the latest drought, with sudden changes between the periods of recharge and drawdown of the aquifer. In the social context, field diagnostics with local stakeholders revealed how the wells installation changed the dynamics of the activities developed by the rural communities. Observed effects were the increase of the number of families and the development of local economics. The heterogeneity of this environment and of its water users requires efficient management policies adapted for the local physical and socioeconomic conditions to avoid overexploitation and maintain the recharge of the aquifers.</p>
<p>The Brazilian semi-arid region presents fragility in terms of surface and groundwater resources due to the irregularity in precipitation regimes and the high evaporation rates. In this context, the communities and the stakeholders are conditioned to seek strategies to cope with droughts, and groundwater emerges as&#160; an alternative supply. This demand requires detailed studies to understand fissural aquifers, given the circulation and storage of water in these aquifers is subject to the presence of structural discontinuities, in particular, influencing the variation of hydrodynamic characteristics and the salinity of wells. The area object of this study corresponds to the Forquilha and Vista Alegre Catchments, in the Cear&#225; State, Northeast Brazil. The present research performed the identification and automatic extraction of the structural lineaments through remote sensing. PALSAR MDE images with 12.5 m spatial resolution and technical data from wells drilled in the region were used. This method promoted the identification of areas of interest for groundwater prospecting. The basins present intermittent drainages and low hydrogeological vocation. Lineaments with preferential NE-SW striking and WNW-ESE striking, in a secondary way, were identified, mainly associated with the drainages of the region. In Vista Alegre the relationship between flow rates and lineaments show a direct affinity. The wells reveal higher flow rates in the western region of the basin, where there is a zone of greater intersection of lineaments, moderate salinity and low variation of the static level in the rainy season. Preliminary results indicate poor interaction between surface and groundwater dynamics. At Forquilha, the relationship between structural features and the most productive wells occurs between structural intersections and drainage. Salinity and static level variation present direct interference in the rainy season, which is reflected in the reduction of the electrical conductivity. In this case, the interaction between the structures and the drainages is more coherent with respect to the lineaments, drainage direction and local relief. Therefore, knowing the structural context of a basin is a necessary increment for a more efficient and planned exploitation of groundwater resources, especially in semi-arid regions that are highly vulnerable to climate change.</p>
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