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Hydrological methodologies are the most efficient approaches for environmental flow (eflow) assessments. This paper presents a hydrological methodology for determining eflows in rivers with scarce development to promote proactive environmental water allocations that limit flow alteration and unsustainable water use. The analysis includes the natural intra-annual and inter-annual ranges of flow variability. Eflows are determined based on four hydrological low-flow conditions and a flood regime. The main contribution is that the flow regime components are adjusted to a four-tiered environmental objective class system based on a novel "frequency-of-occurrence" approach. The method is applied in three rivers in western Mexico with highly variable flow regimes. The eflows are largely (96%) within the central range of previous implementations, and the outcomes reveal an overall good and acceptable level of the method's performance (for 83% of the cases R2 ≥ 0.84, slope = 1 ± ≤ 0.2), consistent with supporting indices of flow variability. [ABSTRACT FROM AUTHOR]

This paper discusses the effects of long-term environmental change (represented by the abundance or scarcity relative to the long-term average level of crop yield/river flow) and short-term environmental shock (represented by the maximum number of consecutive years below the median crop yield/river flow per decade) on population redistribution in Mexico and Ethiopia. Crop production and water resources, which are affected by climate change and influence human survival and activities, were selected as research variables. Two developing countries, namely, Mexico and Ethiopia, were selected as comparison cases. The results showed that short-term environmental shocks had no correlation with population redistribution. Short-term environmental shocks might fail to influence migration decisions or cause only temporary displacements that cannot be detected by demographic statistics. Among the long-term environmental change factors, only crop yield deviation was found to have a significant positive correlation with population redistribution. Based on two different datasets and two different decades, crop yield deviation is positively correlated with population redistribution; the correlation coefficients between crop yield deviation and population redistribution were 0.134 to 0.162 in Mexico and 0.102 to 0.235 in Ethiopia. When urbanization was considered as the control variable, the correlation coefficient between crop yield deviation and population redistribution in Mexico dropped by half, while it was almost the same in Ethiopia. However, Ethiopia's population redistribution was more clearly influenced by the population itself. Crop yield deviation relative to water flow deviation meant changes in livelihoods. Population redistribution is a possible means of adapting to changes in livelihood. Mexico exhibited high resilience to changes in livelihoods caused by long-term environmental change, especially in its densely populated areas. In contrast, Ethiopia was characterized mainly by high population growth and low population migration. People in some areas of Ethiopia were forced to endure hardship of livelihood deterioration or to stay where they were due to the difficulty of obtaining sufficient resources to afford the cost of migration. [ABSTRACT FROM AUTHOR]

This paper deals with the calculation of a set of inflow and volume values for several return periods for the hydrometric station Huites, Sinaloa, Mexico, by means of the numerical closed and open methods to find the roots for an equation; in this case the bisection algorithm and the Secant method, respectively. The bivariate distribution function for the analyzed variables was a two population Gumbel whose parameters were obtained in a previous research by using a genetic algorithm. The bisection algorithm showed to be the most efficient in estimating volume, resulting in a useful tool which allowed for the estimation of the design events with relative simplicity and could be applied in functions of random variables. [ABSTRACT FROM AUTHOR]

Abstract: The twin facets of urban hydraulic reach – cities’ appropriation of water from surrounding regions and irrigation use of urban wastewater over a growing rural footprint – form an emerging global policy challenge, especially as democratizing societies seek institutional means to address both urban growth and water scarcity. A central concern of this paper is to demonstrate that policy regionalism, as a process-based understanding of institutions and decision-making, better explains the causes, forms, and outcomes of hydraulic reach than do more structural approaches. Hermosillo, Mexico presents an unfolding case of rural–urban tension for control over rivers and aquifers as well as the infrastructure for water capture, storage, conveyance, and wastewater release. The analysis employs process documentation of water transfer and wastewater negotiations through interviews, review of primary documents, and field observations. Hermosillo’s recourse to negotiated agreements and quasi-market transactions, led by an emerging group of public sector innovators, advances understanding of water policy in Mexico by moving beyond prevailing concerns with the water reform’s neoliberal underpinnings to exploration of rapidly changing urban-centered experimentation. We conclude that evolving urban–rural power disparities and water resource landscapes of urban growth will drive continued expansion of hydraulic reach in water-scarce regions globally. [Copyright &y& Elsevier]

Copyright of Ingeniería Hidráulica en México is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ingeniería Hidráulica en México is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tropical cyclone (TC) landfall is often accompanied by storm surges, strong winds, and heavy rain that cause destructive flash floods, especially in mountainous regions. However, there is limited understanding of the contribution of TCs to major flood events, especially in Western Mexico. In this study, we assess the contribution of TCs to the annual rainfall, extreme rainfall and stream flow in the mountainous region of Colima, one of the most TC‐exposed areas in Western Mexico. The top 1% of daily rainfall and stream flow, annual maximum rainfall and the highest 20 stream flow events from 1970 to 2015 are examined for their association to TCs. Results indicate that the relative contribution of TCs to the average annual rainfall can exceed 25% in the coastal area of Colima. Over 25–35% of heavy daily rainfall (top 1% rainfall) recorded in the coastal rain gauges is found to be associated with TCs. In terms of high flow, approximately 20–24% of the top 1% flow events and 28–35% (~7 events) of the top 20 flow events are driven by TCs. The heaviest precipitation and high flow events occur typically in the late TC season (September and October). Our results provide insights on the role of TCs in inducing rainfall and stream flow relevant for water and flood risk management. [ABSTRACT FROM AUTHOR]

Geomorphic and hydraulic units in river channels are closely linked to geodiversity and habitats, and thus to biodiversity. In a ~ 200 km reach of the lower Sabine River, in the northern Gulf of Mexico Coastal Plain, 72 different hydraulic units (HU) were identified in six geomorphic zones or river styles. Richness-area relationships indicate a linear or logarithmic increase of HUs, as opposed to the less steep power functions generally found in biogeographic species-area curves or in soil richness-area analyses. Different results are obtained when starting from the upstream or downstream end of the study area, indicating the importance of directionality in such analyses. These results show that HUs (and related habitats and biotopes) are both richer and more variable than a repeated sequence of units. The number of HUs inundated increases linearly with flow stage categories, indicating the importance of high within-bank flows in maintaining and activating HUs. Aggregated HUs (AHUs) associated with similar geomorphic units are highly connected, both with respect to patterns of spatial adjacency and potential connectivity at similar flow levels. Spectral graph theory metrics applied to a graph representation of spatial adjacency shows a highly complex network with a high potential for rapid propagation of changes-and even more so for a graph based on flow connectivity. The flow connectivity graph shows far higher synchronization as indicated by algebraic connectivity. Thus suggests more rapid and coherent changes for processes driven by river flow, as opposed to phenomena driven by other factors between flow events. These findings have important implications for understanding relationships between geodiversity and habitat diversity, managing habitat and biodiversity, and linking the latter to instream flows. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Coastal Research is the property of KnowledgeWorks Global, Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The importance of the chemical composition in evaluating groundwater flow is discussed. Two different geological environments, a felsic volcanic region around San Luis Potosí (SLPB), Mexico, and a sedimentary basin, part of the Pannonian Basin (PB), in Hungary, were chosen to explore the effect of local, intermediate and regional groundwater flows on the chemical evolution of water in different geological circumstances. In the study areas contrasting stable isotopes and groundwater temperature values, as well as the chemical composition of groundwater were convenient tools to propose groundwater flow direction and to study contamination processes in the different groundwater flow systems. Results indicate that regardless of the geological framework variability of the chemical composition of the shallow (<100 m) groundwater is significant; at depth the chemical content of groundwater becomes homogeneous, and the concentrations are smaller than at shallow depths. The Cl– and NO– 3 concentrations indicate mainly up-and downward vertical flow directions suggesting local flow systems in the shallow layers. The linear regression between Cl– and Na+ suggests that evaporation processes are the main control of the Cl– concentration. Deviations from the regression line suggest processes such as pollution at shallow depths in both study areas. Based on the distribution of Ca+2, Mg+2 and Na+, a lateral flow can be traced. The large dimensions of the geological units involved with the regional flow systems implies a long groundwater flow path, also these flows remain isolated from anthropogenic contamination, then groundwater has not been altered by human influence, although in the SLPB a communication between the local and intermediate flows has been found. [ABSTRACT FROM AUTHOR]

Desert aquatic systems are widely separated, lack hydrologic connections, and are subject to drought. However, they provide unique settings to investigate distributional patterns of micrometazoans, including rotifers. Thus, to understand rotifer biodiversity we sampled 236 sites across an array of habitats including rock pools, springs, tanks, flowing waters, playas, lakes, and reservoirs in the Chihuahuan Desert of the USA (n = 202) and Mexico (n = 34) over a period of >20 years. This allowed us to calculate diversity indices and examine geographic patterns in rotifer community composition. Of ~1850 recognized rotifer species, we recorded 246 taxa (~13%), with greatest diversity in springs (n = 175), lakes (n = 112), and rock pools (n = 72). Sampling effort was positively related to observed richness in springs, lakes, rivers, and tanks. Nestedness analyses indicated that rotifers in these sites, and most subsets thereof, were highly nested (support from 4 null models). Distance was positively correlated with species composition dissimilarity on small spatial scales. We predicted species richness for unsampled locations using empirical Bayesian kriging. These findings provide a better understanding of regional rotifer diversity in aridlands and provide information on potential biodiversity hotspots for aquatic scientists and resource managers. [ABSTRACT FROM AUTHOR]

Mangrove forests are ecologically and economically valuable resources composed of trees morphologically and physiologically adapted to thrive across a range of habitats. Although, mangrove trees have high dispersion capacity, complexity of hydrological systems may lead to a fine-scale genetic structure (FSGS). The Transverse Coastal Corridor (TCC) is an interesting case of hydrological systems from fresh to marine waters where mangrove forests dominate. We evaluated genetic diversity and structure of Rhizophora mangle across a range of hydrological conditions within the TCC using inter-simple sequence repeat molecular markers. Sampling included four hydrological systems, two localities inside each system, and fringe and dwarf trees. Genetic differentiation was evaluated at local (<100 km) and fine (<10 km) scales through a set of analyses, and genetic diversity was evaluated at all scale levels and between fringe and dwarf physiognomic types. Rhizophora mangle exhibited a high genetic structure at both scales with high genetic diversity. The genetic structure observed among hydrological systems likely reflects the historical dispersion of mangroves, whereas the FSGS reflect contemporary processes such as seed dispersal restriction, habitat fragmentation, and local water flow regimes. A higher genetic diversity for dwarf than for fringe trees and differentiation between both physiognomic types at a fine-scale were observed and discussed. [ABSTRACT FROM AUTHOR]

This article provides an ethnographic example of a practice-based approach to water governance. It presents the situated case study of a canalero (canal operator) in the everyday water distribution of an irrigation system in Western Mexico. The canalero represents the low-ranked field operators at the frontline of many water provision organizations around the world, thereby providing a wider relevance to this case study. In spite of different waves of modernization that aimed to reduce 'the human element' and control water flows from a distance, canaleros still operate the manually adjustable gates and intakes in many medium and large open canal irrigation systems. Through a precise documentation of the daily routines of administering water, money, and data flows, anticipating shortages and mediating between conflicting demands, we conceptualize their semi-autonomous field of competent action. In contrast to a rule-based or normative approach to water governance, we will argue that the canaleros' cognition and competencies in mediating multiple resource flows are embodied and situated in specific social, technical and spatial arrangements for water provision. However, this field of professional competence is not clearly delineated and gets regularly contested in practice. The water operators deal with these 'problems of control', by drawing on their situational knowledge and embodied cognition acquired on-the-job. This case study outlines a framework for a practice-based and decentered study of water governance, focused on cognitive processes in water provision arrangements. [ABSTRACT FROM AUTHOR]