Drainage in tropical peatlands increases CO.sub.2 emissions, the rate of subsidence, and the risk of forest fires. To a certain extent, these effects can be mitigated by raising the water table depth ...(WTD) using canal or ditch blocks. The performance of canal blocks in raising WTD is, however, poorly understood because the WTD monitoring data are limited and spatially concentrated around canals and canal blocks. This raises the following question: how effective are canal blocks in raising the WTD over large areas? In this work, we composed a process-based hydrological model to assess the peatland restoration performance of 168 canal blocks in a 22 000 ha peatland area in Sumatra, Indonesia. We simulated daily WTD over 1 year using an existing canal block setup and compared it to the situation without blocks. The study was performed across two contrasting weather scenarios representing dry (1997) and wet (2013) years. Our simulations revealed that, while canal blocks had a net positive impact on WTD rise, they lowered WTD in some areas, and the extent of their effect over 1 year was limited to a distance of about 600 m around the canals. We also show that canal blocks are most effective in peatlands with high hydraulic conductivity. Averaging over all modeled scenarios, blocks raised the annual mean WTD by only 1.5 cm. This value was similar in the dry (1.44 cm) and wet (1.57 cm) years, and there was a 2.13 fold difference between the scenarios with large and small hydraulic conductivities (2.05 cm versus 0.96 cm). Using a linear relationship between WTD and CO.sub.2 emissions, we estimated that, averaging over peat hydraulic properties, canal blocks prevented the emission of 1.07 Mg ha.sup.-1 CO.sub.2 in the dry year and 1.17 Mg ha.sup.-1 CO.sub.2 in the wet year. We believe that the modeling tools developed in this work could be adopted by local stakeholders aiming at a more effective and evidence-based approach to canal-block-based peatland restoration.
El objetivo de esta investigación es interpretar las respuestas magnéticas y gravimétricas del subsuelo en la porción oeste en la cuenca Grijalva, México, para identificar y delimitar las áreas de ...unidades de rocas con potencial acuífero. Para ello, se realizó el procesamiento de datos aeromagnéticos y gravimétricos satelitales con el propósito de delimitar las características geológicas de mayor interés. Los resultados muestran que la parte centro-norte de la porción de estudio representa la zona con mayor potencial acuífero, y coincide con las áreas de mayor espesor sedimentario, de menor altitud y donde se concentran las concesiones de agua subterránea. Por tanto, el cambio de gradientes entre las respuestas magnéticas y gravimétricas favorecen el conocimiento del marco estructural (fallas, fracturas, bordes y contactos geológicos) y la inferencia de las áreas con potencial acuífero. En detalle, de las trasformaciones o filtros utilizados la Derivada Tilt (TDR, por sus siglas en inglés) presenta las tendencias lineales asociadas al marco estructural con particular interés hídrico. Se busca favorecer la toma de decisión y la investigación en los temas geohidrológicos, ordenamiento territorial y políticas públicas relacionadas.
The goal of this research is to interpret the magnetic and gravimetric responses subsurface in the western portion of the Grijalva basin, Mexico, in order to identify and delimit the areas of rock units with aquifer potential. For it, the processing of satellite aeromagnetic and gravimetric data was carried out with the purpose of delimiting the geological characteristics of greatest interest. The results show that the north-central part of the study portion represents the area with the greatest aquifer potential, and it coincides with the areas of greater sedimentary thickness, of lower altitude, and where the groundwater concessions are concentrated. Therefore, the change of gradients between magnetic and gravimetric responses contributes to the knowledge of the structural framework (faults, fractures, edges, and geological contacts) and the inference of areas with aquifer potential. In detail, from the filters used, the Tilt Derivative (TDR) presents the linear trends associated with the structural framework of a specific water interest. It seeks to promote decision-making and research on geohydrological topics, territorial planning, and related public policies.
El cálculo de la recarga potencial es un aspecto esencial en la gestión de recursos hídricos, planeación del desarrollo urbano/agrícola y la definición de las tasas de bombeo, a fin de prevenir o ...mitigar la sobreexplotación de acuíferos. En el Valle de Toluca, las altas tasas de extracción han inducido descensos piezométricos acompañados de un desbalance hídrico, al rebasar el volumen de recarga media anual. En este estudio, se desarrolló un balance de humedad del suelo a paso de tiempo 24 horas para la estimación de la recarga potencial histórica y futura. El periodo de análisis comprende de 1980 a 2021, y una proyección hasta 2050 con base en tres escenarios probables de precipitación, temperatura y crecimiento urbano. Los resultados indican un volumen promedio anual de recarga de 369.5 Mm3 con una tasa de 174.5 mm/año, alcanzando los 355.7 mm/año en épocas húmedas. La distribución espacial sugiere una recarga condicionada mayormente por la climatología en las zonas montañosas, mientras que, en el centro del Valle, se asocia con la modificación del uso del suelo. La expansión de la mancha urbana se posiciona como factor preponderante en el aumento de la escorrentía y el gradual decremento de la intercepción y la evapotranspiración real. La disminución en la recarga es una constante en los potenciales escenarios de recarga futura, en comparación con el histórico promedio, se proyecta un cambio negativo de 16.59%, 19.99% y 22.61% para los escenarios bueno, moderado y malo respectivamente. Las tasas de recarga potencial obtenidas constituyen un parámetro inicial en modelos de flujo y análisis regionales de la cuenca.
Estimating potential recharge is essential to water resource management, urban/agricultural development planning, and the definition of pumping rates to prevent or mitigate aquifer overexploitation. In the Toluca Valley, high extraction rates have induced piezometric declines accompanied by a water imbalance exceeding the average annual recharge volume. In this study, a daily soil moisture balance was developed for estimating historical and future potential recharge. The analysis period includes 1980 to 2021 and a projection until 2050 based on three probable scenarios of precipitation, temperature, and urban growth. The results indicate an average annual recharge volume of 369.5 Mm³ with a 174.5 mm/year rate, reaching 355.7 mm/year in wet seasons. The spatial distribution suggests a recharge conditioned in the mountainous areas mainly by the climatology and in the center of the Valley by the land use modification. Urban sprawl is a significant factor in increased runoff and the gradual decrease in interception and actual evapotranspiration. The decrease in recharge is a constant in the potential future recharge scenarios. Compared to the historical average, a negative change of 16.59%, 19.99%, and 22.61% is projected for the best, moderate, and bad scenarios, respectively. The potential recharge rates obtained are an initial parameter in regional basin flow models and analyses.
El bombeo excesivo de agua subterránea en el Valle de Toluca, México, ha derivado en subsidencia regional y manifestación de fracturas en los últimos 20 años. La exposición y crecimiento de tales ...discontinuidades provoca daños a la infraestructura y pérdidas económicas. En el presente estudio se analiza la configuración de la estructura geológica de la cuenca, los gradientes piezométricos desde 1975 y su posible influencia en la generación de fracturas. Se elaboró un modelo geológico tridimensional a partir de los registros de los pozos y secciones transversales existentes. Los datos estratigráficos fueron reinterpretados y clasificados para definir capas con características hidráulicas y mecánicas similares. Las cargas hidráulicas se simularon mediante un análisis geoestadístico para el periodo de 1975-2018. Los resultados de la piezometría reflejan los mayores gradientes negativos en zonas aledañas a las fracturas. El modelo geológico de 14 capas muestra un acuífero fracturado altamente irregular, principalmente en el área que subyace el centro de la ciudad de Toluca y la colonia San Pedro Totoltepec. La presencia de domos volcánicos, la existencia de materiales susceptibles a la consolidación, así como la ubicación de descensos piezométricos en zonas aledañas a las rupturas, se sugieren como los factores que controlan la localización y generación de fracturas. El modelo geológico obtenido en este estudio consistirá la base de futuros modelos de flujo subterráneo.
Excessive groundwater pumping in the Toluca Valley, Mexico, has resulted in regional subsidence and manifestation of ground fissures in the last 20 years. Such discontinuities result in damage to infrastructure and economic losses. This study evaluates the geological structure of the basin, the distribution of piezometric gradients, and its influence on the generation of faults and fractures. A regional three-dimensional geological model was developed using driller’s logs and published cross-sections. Stratigraphic data have been reinterpreted and classified to defined layers with similar hydraulic and mechanic characteristics. The hydraulic-head distributions were replicated through geostatistical analysis for the period 1975-2018. Piezometry results reflect the highest negative gradients in areas near fractures. The 14 layers geologic model show a highly irregular fractured aquifer specially under the Toluca city center and San Pedro Totoltepec location. The presence of volcanic domes, the existence of materials susceptible to consolidation, in addition to the location of piezometric descents in areas around the ruptures, are suggested as characteristic factors controlling the location and generation of faults and fractures. The geological model obtained in this study will be applied to support future groundwater flow modelling.
The carbon (C) dynamics of northern peatlands are sensitive to hydrological changes owing to ecohydrological feedbacks. We quantified and evaluated the impact of water level variations in a beaver ...pond (BP) on the CO.sub.2 flux dynamics of an adjacent, raised Sphagnum-shrub-dominated bog in southern Canada. We applied the CoupModel to the Mer Bleue bog, where the hydrological, energy and CO.sub.2 fluxes have been measured continuously for over 20 years. The lateral flow of water from the bog to the BP was estimated by the hydraulic gradient between the peatland and the BP's water level and the vertical profile of peat hydraulic conductivity. The model outputs were compared with the measured hydrological components, CO.sub.2 flux and energy flux data (1998-2019). CoupModel was able to reproduce the measured data well. The simulation shows that variation in the BP water level (naturally occurring or due to management) influenced the bog net ecosystem exchange (NEE) of CO.sub.2 . Over 1998-2004, the BP water level was 0.75 to 1.0 m lower than during 2017-2019. Simulated net CO.sub.2 uptake was 55 gCm-2yr-1 lower during 1998-2004 compared to 2017-2019 when there was no BP disturbance, which was similar to the differences in measured NEE between those periods. Peatland annual NEE was well correlated with water table depth (WTD) within the bog, and NEE also shows a linear relation with the water level at the BP, with a slope of -120 gCO2-Cm-2yr-1m-1. The current modelling predicts that the bog may switch from CO.sub.2 sink to source when the BP water levels drop lower than â¼ 1.7 m below the peat surface at the eddy covariance (EC) tower, located on the bog surface 250 m from the BP. This study highlights the importance of natural and human disturbances to adjacent water bodies in regulating the net CO.sub.2 uptake function of northern peatlands.
Hidrodinámica regional de Los Ríos, Tabasco, México González-Herrera, Roger; Cámara-Yamá, Iván; Sánchez y Pinto, Ismael
Boletín de la Sociedad Geológica Mexicana,
01/2022, Letnik:
74, Številka:
2
Journal Article
La interacción del agua subterránea con el agua superficial es importante para estudiar los flujos tanto físicos como químicos en el ciclo hidrológico. Los sistemas de agua subterránea y agua ...superficial se han estudiado, por lo general, de manera separada, lo que dificulta la cuantificación de los flujos existentes entre ellos. Sin embargo, cada vez más se reconoce la importancia de entender cómo influye esta interfase en los balances hidrológicos, los ciclos geoquímicos, los ecosistemas y el cambio global. Para contribuir a este entendimiento, se llevó a cabo un estudio de la hidrodinámica regional de la zona de Los Ríos, Tabasco, México, en el que se siguió un enfoque de investigación de campo para estimar las interacciones entre el agua superficial y subterránea. El objetivo fue determinar la naturaleza actual de la interacción del agua subterránea con el agua superficial en la zona de estudio, enfocándose en la cuantificación del flujo de agua subterránea con base en información histórica. El análisis de los datos piezométricos indica que los gradientes hidráulicos son altos y sugiere tasas de recarga altas hacia los cuerpos de agua superficiales, incrementando significativamente el caudal de las corrientes. Se logró delimitar las zonas de recarga y descarga de aguas subterráneas utilizando una red de flujo.
Groundwater-surface water interaction is important to study both physical and chemical flows in the hydrological cycle. Groundwater and surface water systems have generally been studied separately, making the flows between them difficult to quantify. However, the importance of understanding the influence of this interface on hydrological balances, geochemical cycles, ecosystems, and global change, is increasingly recognized. To contribute to this understanding, a study of the regional hydrodynamics of the Los Ríos area, Tabasco, Mexico, was conducted. A field research approach was followed to estimate the interactions between surface water and groundwater. The objective was to determine the current nature of the interaction of groundwater with surface water in the study area, and focused on quantifying the former’s flow based on historical information. The analysis of the piezometric data indicates that the hydraulic gradients are high, suggesting high recharge rates towards the surface water bodies that increase streamflow rates significantly. The groundwater recharge and discharge zones were delimited using a flow network.
•Track the evolution of the inverse methods over the last decades in hydrogeology.•Discuss issues encountered in the inverse problem, e.g., handling multiGaussianity, and considering prior ...statistics.•Reveal the development motivation of the inverse methods and their recent trends.
Parameter identification is an essential step in constructing a groundwater model. The process of recognizing model parameter values by conditioning on observed data of the state variable is referred to as the inverse problem. A series of inverse methods has been proposed to solve the inverse problem, ranging from trial-and-error manual calibration to the current complex automatic data assimilation algorithms. This paper does not attempt to be another overview paper on inverse models, but rather to analyze and track the evolution of the inverse methods over the last decades, mostly within the realm of hydrogeology, revealing their transformation, motivation and recent trends. Issues confronted by the inverse problem, such as dealing with multiGaussianity and whether or not to preserve the prior statistics are discussed.
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