Fissure Flow Research Articles

How do belowground bedrock fissures impact soil erosion on karst hillslopes under different rainfall intensity conditions?

AbstractIn karst regions, bedrock fissures are developed via karstification, which may cause belowground soil erosion (BSE). However, few studies have quantitatively assessed the effect of bedrock fissures on BSE because BSE measurement is difficult on karst hillslopes. The objective of this study was to investigate the differences in runoff and soil erosion at the surface and belowground on karst hillslopes with and without bedrock fissures (hereafter called HS1 and HS2, respectively) under different rainfall intensities (50, 75, and 100 mm hr−1). The slope gradient was 5°. In the rainfall process, surface runoff (SR), subsurface runoff (SBR), soil–rock interface flow (SRIF), and underground fissure flow (UFF) data were collected on HS1 and HS2. The results showed that the SR coefficients of HS1 and HS2 were negligible (less than 1%) under rainfall intensities of 50 and 75 mm hr−1, and UFF (56%–57%) of HS1 and SRIF (40%–44%) of HS2 dominated the runoff pattern. Under a rainfall intensity of 100 mm hr−1, the SR coefficient increased to approximately 30% under the two treatments, and the coefficients of UFF of HS1 and SRIF of HS2 decreased to 29% and 24%, respectively. Compared to HS2, UFF of HS1 increased by 18%–39%. The SBR coefficient was lower than 10% for all rainfall events. Because SR and SBR were low under rainfall intensities of 50 and 75 mm hr−1, the soil loss was dominated by UFF (99%–100% of the total sediment) of HS1 and by SRIF (86%–97% of the total sediment) of HS2. Under the 100 mm hr−1 rainfall intensity, almost all sediment was lost via SR under the two treatments, and the sediment loss of HS2 was 33% higher than that of HS1. Our results indicated that bedrock fissures caused more underground rainwater leakage at the SRI and further decreased surface soil erosion on karst hillslopes.

Evidence of karstification in chalk and limestone aquifers connected with stream systems and possible relation with the fish ecological quality ratio in Denmark

Although chalk aquifers are not too often associated with conduit flow, they are highly productive groundwater systems and, like limestone aquifers, they can be vulnerable to contamination when exposed to land use activities. The Danish carbonate rocks are generally recognized to be highly fractured and covered by thick Quaternary sediments. Fissure flow is pronounced, occurring in the upper 50–100 m due to Pleistocene glaciations. According to recently published maps of the distribution of karst in Europe, Denmark has no karst. However, this study concludes that karstified chalk and limestone aquifers are an important source of freshwater in Denmark. Four national datasets on karst features, groundwater flow, groundwater chemistry, and fish ecological quality ratio (EQR) data now indicate more heterogeneous structures and preferential flow pathways in the chalk and limestone aquifers than had been conceptualized and modelled with a national water resources groundwater/surface-water model in the recent past. This study provides new qualitative evidence that rapid and preferential flow of water and agrochemicals from the surface through thinner parts of the Quaternary cover layers, sinkholes and solution-enlarged fractures may likely impact the vulnerability of chalk and limestone aquifers. Additionally, due to the preferential flow system, some gaining streams discharged by karstified chalk and limestone aquifers show increased fish EQR values when using observed river daily discharge data instead of simulated daily discharge.

Role of the preferential flow at rock–soil interface in the water leaking process in near-surface fissures filled with soils in the karst rock desertification area

Soil preferential flow infiltrating rapidly through the rock–soil interface is an important hydrological process in karst rocky desertification area. However, how does the water leakage in the near-surface fissures, especially those filled with soil, proceed? The role of preferential flow at rock–soil interface of those fissures on water leakage process still puzzles us. The goal of this study was to reveal the role of soil preferential flow at the rock–soil interface in the process of water leaking of near-surface fissures. Five typical types of near-surface fissures were selected in an area experiencing severe rocky desertification in Guizhou Province, China. Dye tracer testing was applied, combined with digital image processing techniques. The results indicated that the rock–soil interface flow on both sides of the fissures is the most important preferential flow form in the fissures in karst area. The dyed area ratio of preferential flow varied from 0.12 to 0.48 in the rock + soil profiles, from 0.06 to 0.37 in the soil profiles, and between 0.02 and 0.16 in the rock–soil interface. The rock–soil interface is the smallest in terms of both their variation range of dyed area ratio and preferential flow patterns compared with soil and rock–soil profiles. The soil preferential flow in near-surface fissures mainly occurs in the soil depth range of 0–20 cm. The preferential flow path is mainly affected by the rock–soil interface on both sides and can pass through the clay layer with poor permeability. However, the soil depth of the dyed part was more than 50 cm. The soil preferential flow at the rock–soil interface is the main form of rapid downward leakage of water in near-surface fissures in the karst rocky desertification area, which can flow to the bottom of clay layer with poor permeability.

Rainwater transformation to runoff and soil loss at the surface and belowground on soil-mantled karst slopes under rainfall simulation experiments

Karst slopes have thin soil layers covering bedrock and feature multiple near-surface soil-rock interfaces (SRIs), which can produce hydrological processes that differ from those of nonkarst slopes. This study investigated the differences in the proportions of rainwater transformed into surface and belowground runoff and measured soil loss on soil-mantled karst slopes with different hydrological situations: bedrock with fissures (HS-1) and without fissures (HS-2). The rainfall intensity was 50 mm/h. Three slope gradients (5°, 15° and 25°) were applied, and surface runoff (SR), subsurface flow (SF), underground fissure flow (UFF) and soil-rock interface flow (SRIF) were collected during rainfall. No SR was produced on 5° slopes in either treatment. The proportion of rainwater absorbed by soil (RH) was approximately 34%-46% of the rainwater, with no significant differences (p > 0.05) between HS-1 and HS-2. On the 5° and 15° slopes, 28%-61% of the rainwater was transformed into UFF under HS-1, and 29%-50% of the rainwater was transformed into SRIF under HS-2. On the 25° slope, the SRIF and UFF proportions were<18%. Bedrock fissures greatly affected the type of runoff but had little effect on the near-surface soil water. The SR and SF amounts were 29%-67% and 3%-38% higher in HS-2 than in HS-1, respectively. Due to bedrock fissures, on average, 6% of rainwater was lost as underground flow during rainfall, and the extra rainwater, 30% on average, flowed along the SRI underground, potentially forming UFF. This difference occurs because the infiltrating rainwater that reaches the SRI can freely drain through bedrock fissures in HS-1 but not in HS-2. The soil loss via SF, SRIF and UFF was very low (<0.05 g/L). Therefore, slope gradients and bedrock fissures both have major effects on rainwater transformation, and soil loss via rainfall impact is very slow on soil-mantled karst slopes.

Progresses of weathered bedrock ecohydrology in the Earth&amp;rsquo;s critical zone

<p indent="0mm">Weathered bedrock is crucial in the Earth’s critical zone, which connects soil moisture dynamics and shallow groundwater recharge, and therefore plays an essential role in the ecohydrological cycle on the terrene surface. The exchangeable water stored in weathered bedrock is an essential source of water that is different but parallel to soil water or groundwater. This water in the weathered bedrock, namely, rock moisture, is much greater than that in the soil, which is a pivotal and stable water source for plants, especially in dry years or arid and semiarid areas. When rainfall occurs, the infiltration and lateral flow of water are not limited to the soil layer. The rainwater that infiltrates by piston flow and preferential flow can pass through the fractured or weathered bedrock layer and collect at the fresh bedrock interface to form groundwater. Then, it flows laterally to adjacent river channels, where it also plays an important role in the distribution of evapotranspiration and runoff. Moreover, after weathered bedrock water storage accumulates to its maximum in the rainy season, the additional rainwater becomes base flow in the form of runoff or fissure flow. However, research on the ecohydrological cycle of the terrestrial surface layer has long focused on vegetation water absorption, surface soil moisture, and groundwater replenishment. Little attention has been given to the ecohydrological changes in the weathered bedrock layer and their external effects, and review articles are relatively scarce. Therefore, to clarify the latest research progress on weathered bedrock ecohydrology, the relevant documents collected in the Web of Science core collection database and the China National Knowledge Infrastructure (CNKI) journal database in the past 30 years were retrieved. The developments of the current focuses of research and potential research directions were quantitatively visualized using VOSviewer and bibliometrics, and the potential influential pathways of weathered bedrock ecohydrology were then drawn. The results show that weathered bedrock ecohydrological research is interdisciplinary and has a rich theoretical foundation of geology, water resources, environmental science ecology, and engineering. The number of published articles has gradually increased annually, and major mainstream Earth science journals wish to report these new findings; however, there is room for expansion and discussion in the international arena. The research area in this field mainly uses a shallow overlying soil layer, such as karst, as the platform and focuses on the karst hydrological model, the distribution of hydrological resources, the ecological risk, the lithologic characteristics of vegetation, and the interaction between bedrock and groundwater. Unfortunately, less attention has been given to areas with relatively thick soil layers, such as the hilly valley region. Moreover, ecohydrological effects of weathered bedrock include not only differences in the characteristics but also external disturbances, such as soil water redistribution, groundwater recharge, excretion regulation, and plant growth regulation. Future research might focus on the following: Water storage and its dynamic changes in the bedrock weathered layer, outflow characteristics, the process and mechanism of organism interactions, the process and mechanism of exchange with groundwater recharge, the process of water exchange with the soil-bedrock interface, the action of the vegetation root system and plant growth, and the framework and application of the ecological hydrological model of the atmosphere-vegetation-soil-weathered bedrock-groundwater continuum in the Earth’s critical zone. Furthermore, potential influential pathways of weathered bedrock ecohydrology might be regulating seasonal water shortage by inhibiting soil water infiltration, groundwater runoff, and replenishment; expanding bedrock fissure water storage by increasing animal activity; and transporting water and nutrients by participating in mycorrhizal hyphae. This study might provide a reference for deepening critical zone science, expanding ecohydrology research, and providing rational management for vegetation restoration.

Hydro-Damage Properties of Red-Bed Mudstone Failures Induced by Nonlinear Seepage and Diffusion Effect

Nonlinear catastrophes caused by geological fluids are a fundamental issue in rock mechanics and the geoengineering hazard field. For the consideration of hydrodynamic force on red-bed mudstone softening damage, X-ray visualization tests on the fissure flow in mudstone block failure under hydrodynamic force was performed in this study based on block scale, and the physical phenomena of fissure seepage and nonlinear diffusion were further explored. A new method for evaluating the hydro-damage degrees of rocks using an X-ray image analysis was proposed, and the quantitative relation of diffusion coefficients of hydro-damage and seepage was established. The research results revealed that the hydrodynamic force promoted the fluid-filled fissure behavior in mudstone specimen failure. Furthermore, the seepage and diffusion phenomena of fluid in rocks during failures were indicated using X-ray imaging. A dual mechanical behavior was presented in the nonlinear seepage and abnormal diffusion of a red mudstone geological body under hydrodynamic conditions. The damaged degree of mudstone was aggravated by the effect of hydrodynamic force, and the initial seepage–diffusion coefficient with respect to lower hydro-damage was larger than the final seepage–diffusion coefficient with respect to higher hydro-damage of rocks with a decreasing nonlinear trend.

Drivers of soil erosion and subsurface loss by soil leakage during karst rocky desertification in SW China

As an extreme manifestation of environmental degradation, karst rock desertification is caused by soil loss and rock exposure. In some areas with serious rocky desertification, there is no soil to be eroded or leaked. The soil loss in these areas superimposes soil erosion and unique subsurface loss by soil leakage through fissures, pipelines, sinkholes, etc., which directly reduce soil resources and accelerate rocky desertification. However, the factors driving soil erosion and subsurface loss by soil leakage are still unclear. Rainfall experiments were conducted on simulated slopes with surface-exposed bedrock and subsurface fissures based on field investigations in a karst rocky desertification area of Guizhou Province, China. Four factors, including rainfall intensity, slope gradient, bedrock exposure rate and subsurface fissure degree, were considered in the experiment. We found that the amount of soil surface erosion and subsurface leakage loss is driven not only by the runoff volume but also by other influential factors. Rainfall intensity is the driving factor determining the amount of surface erosion and subsurface leakage loss of soil and water and the relationship between them. The slope gradient plays a leading role only in subsurface fissure flow leakage loss. The bedrock exposure rate drives the surface soil erosion rate, shows a critical value (30%), and dominates the fissure flow leakage loss rate. Subsurface fissure density plays an important role in the surface loss of soil and water; however, an increase in the subsurface fissure density does not obviously accelerate the subsurface leakage loss of soil and water. Although this result, obtained from laboratory simulations, may differ at the field scale or larger, it could provide a foundation for systematic studies on soil erosion/leakage and insights into the relations between rocky desertification and soil erosion/leakage and their driving factors in karst rocky desertification.

Time-lag characteristics of the response of karst springs to precipitation in the northern China

Atmospheric precipitation is the main source of replenishment for large karst springs in the northern China. The extensive spring area and the high heterogeneity and anisotropy of the karst aquifer can cause a significant lag in the response of spring water level to precipitation. To explore the response characteristics of different flows of groundwater to precipitation, this study took the Jinan spring area as an example and used time series analysis to investigate the response characteristics of spring to rainfall. This study showed that atmospheric precipitation remains the single most important factor affecting spring discharge at present. According to the characteristics of spring discharge recession, the groundwater flows in the Jinan spring area can be divided into conduit-major fissure flow and diffuse-minor fissure flow. This study examined the response characteristics of different groundwater flows to precipitation through correlation and spectral analyses. The response time of conduit-major fissure flow to precipitation ranged 7–16 days and the duration ranged 12–24 days. The response time of diffuse-minor fissure flow to precipitation ranged 36–56 days, and the duration ranged 1–3 hydrological years. Compared with the karst water system in the southern China, the karst water system in the northern China has a stronger regulating effect. On this basis, this study proposed a correlation and spectral analyses and evaluation method suitable for understanding the dynamics of large karst springs in the northern China.

Experimental investigation of the nonlinear evolution from pipe flow to fissure flow during carbonate rock failures

Fissure flow (FF)-induced disasters are a basic scientific difficulty in the fields of rock mechanics and geological engineering disasters. Based on large collapse and landslide disasters in China’s southwestern mountainous karst region, this study focused on the nonlinear evolution of the transition from pipe flow (PF) to FF during the process of carbonate rock rupture, with a view to determining the mechanism by which the interactions between geological structures and karst PF cause disasters. An experiment was designed and conducted to visualize the PF–FF transition in a carbonate rock by X-ray imaging at a material scale. Multiple mechanical metrics for the carbonate rock as well as X-ray imagery of the flow were obtained. The effects of multistage loading on the PF regime and the fractal characteristics of the PF–FF morphology were investigated. On this basis, the mechanism of the nonlinear evolution from PF to FF during the carbonate rock rupture process was determined. The experiment result demonstrates the fractal characteristics of the nonlinear evolution from PF to FF during the carbonate rock rupture process.

Determining the influencing factors of preferential flow in ground fissures for coal mine dump eco-engineering.

Ground fissures (GF), appearing in front of dumps, are one of the most obvious and harmful geological hazards in coal mining areas. Studying preferential flow and its influencing factors in the ground fissures of dumps may provide basic scientific support for understanding the rapid movement of water and vegetation restoration and reconstruction in mining areas. Based on field surveys of ground fissures, three typical ground fissures were selected in the studied dump. The morphological characteristics of preferential flow for ground fissures were determined through field dye tracing, laboratory experiments, and image processing technology. The results indicated that the lengths of the three ground fissures ranged from 104.84 cm to 120.83 cm, and the widths ranged from 2.86 cm to 9.85 cm. All of the ground fissure area densities were less than 10%, and the proportion of ground fissure surface area was small in the dump. The maximum fissure depth was 47 cm, and the minimum was 16 cm. The ground fissure widths ranged from 0 cm to 14.98 cm, and the fissure width and fissure width-to-depth ratios decreased with increasing soil depth. The stained area was greater than 90% in the 0–5 cm soil layers of the three fissures, and water movement was dominated by matrix flow. The stained width decreased from 90 cm to 20 cm with increasing soil depth. The preferential flow was mainly concentrated on both sides of the fissure, which was distributed as a “T” shape. The preferential flow stained area ratios were 27.23%, 31.97%, and 30.73%, respectively, and these values decreased with increasing soil depth. The maximum stained depths of the preferential flow among the three fissures were different, and the maximum stained depth of GF II was significantly larger than that of GF I and GF III (P < 0.05). The stained path numbers of the three fissures ranged from 0 to 49. With increasing soil depth, the stained path number first increased and then decreased. The stained path widths of the three fissures ranged from 0 cm to 90 cm. With the increase in soil depth, the stained path width decreased. The stained area ratio was significantly positively correlated with ground fissure width, the ground fissure width-to-depth ratio, soil saturated hydraulic conductivity, soil organic matter, and sand content and was significantly negatively correlated with soil water content and clay content. The stained path number was significantly positively correlated with ground fissure width, the ground fissure width-to-depth ratio, soil saturated hydraulic conductivity and soil organic matter. The stained path width was significantly positively correlated with the ground fissure width-to-depth ratio, soil saturated hydraulic conductivity, soil organic matter and sand content and was significantly negatively correlated with clay content. Plant roots could significantly increase the stained area ratio, stained path number, and width and promote the formation and development of preferential flow.

Research on Forecasting Model of Daily Discharge in Karst Area Based on Mea Grey Neural Network

The water-bearing system in the karst area is complex and changeable. Water in the water-bearing medium has the characteristics of coexistence of fissure flow and pipeline flow, coexistence of laminar and turbulent flow, coexistence of linear and nonlinear flow, coexistence of continuous flow and isolated water body. In areas where economic development is relatively backward, most areas lack data or no data. Based on the characteristics of the karst area in the southwest, this paper proposes a thinking evolution algorithm to optimize the gray neural network model. This method improves the optimization ability of runoff prediction models and effectively overcomes human neural network learning. The speed is slow and there are inherent shortcomings of local minima. After studying the daily flow forecast of Zhenlong Station, it is shown that the relative error of the prediction is small and can be effectively used for short-term runoff prediction.

Characterizing flow release from the aquifer of Guntur Spring in Gunungsewu Karst Area, Indonesia

Karst aquifers have three flow components, namely conduit, fissure, and diffuse. This research was designed to characterize the flow release from the karst aquifer of Guntur Spring. It is part of the hydrogeological system Panggang Block, part of Gunungsewu Karst Area, Gunungkidul, the Special Region of Yogyakarta. The water level and discharge data from May 2018 to May 2019 were processed to create flow hydrographs. Two different methods were applied to measure discharge variation in one year, namely sudden injection in dry seasons and velocity area in rainy seasons. While baseflow separation analysis was employed to calculate the percentage of baseflow, recession constants computation was used to derive the three flow components of the karst aquifer. The recession constants, Kb (diffuse flow), Ki (fissure flow), and Kc (conduit flow), were calculated from nine selected flood events. From the hydrograph analysis, this research found that the average discharges in rainy and dry seasons were 56.7 l/s and 13.25 l/s, respectively. These relatively small flows are mainly because Guntur Spring is an epikarst spring with layers of limestone or thin aquifer. The recession constants were Kb=0.998, Ki=0.933, and Kc=0.500, meaning that Guntur Spring has three flow components, including diffuse, fissure, and conduit. Although the baseflow separation analysis found that the diffuse flow prevailed (93.07%), the influence of conduit and fissure flows was apparent, especially during rainy seasons. The Guntur Spring hydrograph analysis revealed that the average time to baseflow (Tb) and time to peak (Tp) was rather prolonged. Supporting this finding was the mean value of Kc that categorized the recession as medium and signified that the conduit fractures developing in Guntur Spring were not extensive. As a conclusion, diffuse flow mainly characterizes the discharge of Guntur Spring with some indications of growing fissures and conduits.

Preliminary Characterization of Underground Hydrological Processes under Multiple Rainfall Conditions and Rocky Desertification Degrees in Karst Regions of Southwest China

Karst regions are widely distributed in Southwest China and due to the complexity of their geologic structure, it is very challenging to collect data useful to provide a better understanding of surface, underground and fissure flows, needed to calibrate and validate numerical models. Without characterizing these features, it is very problematic to fully establish rainfall–runoff processes associated with soil loss in karst landscapes. Water infiltrated rapidly to the underground in rocky desertification areas. To fill this gap, this experimental work was completed to preliminarily determine the output characteristics of subsurface and underground fissure flows and their relationships with rainfall intensities (30 mm h−1, 60 mm h−1 and 90 mm h−1) and bedrock degrees (30%, 40% and 50%), as well as the role of underground fissure flow in the near-surface rainfall–runoff process. Results indicated that under light rainfall conditions (30 mm h−1), the hydrological processes observed were typical of Dunne overland flows; however, under moderate (60 mm h−1) and high rainfall conditions (90 mm h−1), hydrological processes were typical of Horton overland flows. Furthermore, results confirmed that the generation of underground runoff for moderate rocky desertification (MRD) and severe rocky desertification (SRD) happened 18.18% and 45.45% later than the timing recorded for the light rocky desertification (LRD) scenario. Additionally, results established that the maximum rate of underground runoff increased with the increase of bedrock degrees and the amount of cumulative underground runoff measured under different rocky desertification was SRD &gt; MRD &gt; LRD. In terms of flow characterization, for the LRD configuration under light rainfall intensity the underground runoff was mainly associated with soil water, which was accounting for about 85%–95%. However, under moderate and high rainfall intensities, the underground flow was mainly generated from fissure flow.

Numerical Simulation of Transient Temperature Field of Single Fissure Flow in Mining Rock Mass

In this paper, the transient temperature field distribution of single fissure water flow is studied in order to study the fluid-solid coupling heat transfer mechanism of the rock mass. By simulating the flow state of underground water flow along single fissure of rock mass, it establishes the seepage model of single fissure. In addition, the mathematical model of temperature field under the influence of seepage field is established by simplifying the equations of single fissure and temperature control. The results show that the heat balance is closely related to temperature difference and time under fluid-solid coupling, and the greater the change of permeability velocity, the greater the change of temperature distribution. With the increase of time and heat transfer, the temperature difference between the water flow temperature and the wall surface of the rock mass gradually decreases, and the temperature isograde change rate along the flow direction of the water flow decreases gradually.

Karst aquifer response by time series analysis applications in Jonggrangan Karst, Java Island, Indonesia

The time series analysis approach has the ability to recognize the characteristics of a karst aquifer by analyzing the response of the discharge from rainfall in a karst area. The karst aquifer is considered to be a system that influences the response to the conduit, fissure, and diffuse flow. This research was conducted in Mudal, Kiskendo, and Anjani Springs located in the Jonggrangan Karst, Java Island, Indonesia. The objective of this study was to determine the differences in the response of karst aquifers in releasing the flow in these three springs. The data used in this study are paired data of discharge and rainfall, which were obtained from January to November 2018 (N data = 31,408). Discharge data were obtained by installing an automatic water level logger, while rainfall data were obtained by installing automatic rain gauges in each spring. The time series analysis methods that were used are cross-correlation, auto-correlation, cross-amplitude, spectral density, phase functions, and gain functions. The master recession curve (MRC) calculation was performed to confirm the results from the time series analysis. The study reveals that each spring has a different response in releasing the flow components. Anjani Spring has the fastest response to conduit and fissure flows. However, this spring has the longest release duration of the diffuse flow component, indicating that a well-developed karst aquifer can also have high system memory and large storage capacity. Kiskendo Spring has a faster conduit and diffuse flow response than Mudal Spring but has the slowest fissure flow response, reflecting the void fissure that dominates in this site. In addition, MRC confirmed the results of the time series analysis calculation. This MRC analysis also shows that the study sites were categorized as a high sensitivity degree of karst aquifer. The karst aquifer’s characterization in this study can be used as basic data in the water resources management in the Jonggrangan Karst.

中梁山岩溶槽谷区不同土地利用方式坡地产流规律

PDF HTML阅读 XML下载 导出引用 引用提醒 中梁山岩溶槽谷区不同土地利用方式坡地产流规律 DOI: 10.5846/stxb201812132723 作者: 作者单位: 西南大学地理科学学院,西南大学,中国地质科学院岩溶研究所,西南大学地理科学学院,西南大学,西南大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0502306）；国家自然科学基金项目（41472239）；西南大学基本科研业务费专项基金项目（XDJK2015C071） Characteristics of different land-use types of slope runoff in a karst trough valley located in Zhongliang Mountain, Chongqing Author: Affiliation: Southwest University,Southwest University,,,, Fund Project: The national key research and developmental program of China (2016YFC0502306);The National Natural Science Foundation of China (41472239);The special fund project of basic scientific research operating expenses of southwest university (XDJK2015C071) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:坡地产流是造成岩溶区水土流失的主要驱动力，研究典型岩溶槽谷区坡地产流规律，对岩溶区防治水土流失、合理利用地下水资源具有重要理论意义。在重庆市中梁山龙凤和龙车槽谷选取不同土地利用方式的4个标准径流小区，对降水、地表径流、壤中流、裂隙流和土壤含水率进行了同步监测，探讨了坡地产流特征。结果表明：（1）4个不同土地利用方式的径流小区，坡地总产流量从大到小依次为：耕地（3696.9L）> 果园地（3657.2L）> 竹林地（2922.9L）> 林地（2211.1L），总径流系数（3.1%-5.2%）远低于非岩溶区（约20%）；（2）4个径流小区的产流形式主要为地表径流，壤中流和裂隙流产生滞后于地表径流；（3）降水因子、前期土壤含水率共同影响地表径流，但降水因子对地表径流的影响远大于前期土壤含水率。降水因子中，15min最大雨强是影响耕地、果园地的地表径流的主要因素，降水量是影响林地、竹林地的地表径流的主要因素；前期土壤含水率对耕地、林地、果园地地表径流影响较大，对竹林地地表径流影响较小。 Abstract:Slope runoff is the most important soil erosion force in karst areas, the properties of which in a typical karst trough valley are of great significance for soil erosion prevention and for groundwater resources management. In this study, four standard runoff plots with different land-use patterns were set in a typical karst trough valley located in the Zhongliang Mountain, Chongqing. Land-uses in the trough valley, were farmland, orchard, bamboo land and forest. Hydrological characteristics, including precipitation, surface runoff, soil-layer flow, fissure flow and soil moisture content, were monitored simultaneously, and then slope runoff properties in the typical karst trough valley were determined by slope runoff plots. The results were:(1) In the four runoff plots, the total runoff coefficient (3.1%-5.2%) was significantly lower than that of non-karst areas (approximately 20%), and the total slope runoff of the four kinds of land-use decreased in an orderly way, with farmland being observed to have the greatest amount (3696.9L), followed by orchards (3657.2L), then bamboo land (2922.9L), and finally forest (2211.1L). (2) Surface runoff was the dominant runoff form in the four runoff plots, and this was followed by soil-layer flow and fissure flow. (3) Precipitation factors and antecedent soil moisture content together affected surface runoff discharge; however, precipitation factors were the predominant factor. Four precipitation factors were involved in the surface runoff formation analysis, in which the maximum intensity of continuous rainfall in 15 minutes was the predominant factor in farmland and orchards, and precipitation was the predominant factor in forests and bamboo land. Meanwhile, the antecedent soil moisture content had relatively greater impact on farmland, followed by forest land and then orchards, than bamboo land. 参考文献 相似文献 引证文献

Role of underground fissure flow in near-surface rainfall-runoff process on a rock mantled slope in the karst rocky desertification area

Because of the complex near-surface double-layer geologic structure (i.e., surface and underground fissures) of slopes in karst regions, it is difficult to collect data on all flows, especially the flows generated in underground fissures. This lack of information leads to a poor understanding of the rainfall-runoff process associated with soil loss in karst landscapes. The goal of this study was to determine the output characteristics of surface, subsurface and underground fissure flows and their conversion relationships, as well as the role of underground fissure flow in the near-surface rainfall-runoff process, using rainfall experiments. The results revealed the following findings. (і) Light rainfall intensities (15 and 30 mm/h) generated subsurface lateral flow and underground fissure flow, whereas greater rainfall intensities generated surface runoff in addition to subsurface and underground flows. (ii) The runoff/drainage depths of all the above flows increased with increasing rainfall intensity, while the runoff/drainage coefficient exhibited no obvious regular change, except for the surface runoff. Moreover, the distribution ratio of surface runoff to total flow also increased with increasing rainfall intensity but decreased with increasing underground fissure degree, while the distribution ratio of underground fissure flow exhibited the opposite trend. (iii) Underground fissure flow, with distribution ratios of 27.8–78.0%, dominated the total flow yield. This study has significance for controlling soil erosion and water shortage in the karst rocky desertification region and also improves the understanding of the near-surface rainfall-runoff process in this region

Basaltic ring structures of the Serra Geral Formation at the southern Triângulo Mineiro, Água Vermelha region, Brazil

The Serra Geral Formation constitutes a continental magmatic province on the southern part of South America within the Paraná basin. Basaltic magmatism of the Serra Geral Formation occurred as extrusions at around 134.5 to 131.5My ago. The formation is part of the Paraná-Etendeka large igneous province, spanning South America and southwestern Africa. The main extrusion mechanism was probably through fissures related to extensional regime during the breakup of Gondwana in the Cretaceous. Basaltic ring structures (BRS) with tens of meters of diameter, cropping out downstream of Grande river at Água Vermelha hydroelectric dam in southern Triângulo Mineiro region, enable the study of the mechanism of extrusion. The origin of the BRS has been subject to differing interpretations in the past, either collapsed lava flows or central conduits. Detailed geological mapping at 1:1000 scale, stratigraphic, petrographic and gravimetric analysis of the most well preserved of the BRS, with a 200m diameter, has enabled the description of thirteen different basalt lava flows, along with single a central lava lake and a ring dyke structure. The central flow, interpreted as a preserved lava lake, comprises vesicle- and amygdale-rich basalt, spatter, ropy and degassing structures. The most basal of the thirteen lava flows has massive basalt containing geodes filled with quartz. Above, the lava flows show massive basalt with vertical columnar jointing where is possible to identify the top and bottom of each individual flow, with gentle dips towards the perimeter of the structure. A prominent ring dyke dipping towards the lava lake presents horizontal columnar jointing and cuts the basal and central flows. The gravimetric analysis shows a weak negative Bouguer anomaly on the center of the BRS. The proposed model describes the volcanism of the region in three main steps: (1) fissure flow occurs with lava input; (2) this lava cools and crystallizes cementing most of the fissures, promoting the formation of localized central conduits; and (3) the presence of dissolved gas in lava produces ring and radial fractures around the solidified lava lake. The magma uses some of the ring fissures to ascend and the following lava flows assume the ring shape of the dyke vent. Thus, the BRS in Água Vermelha region can be interpreted as remnants of central conduits representing the late stage magmatism of the Serra Geral Formation.

Eruption of magmatic foams on the Moon: Formation in the waning stages of dike emplacement events as an explanation of “irregular mare patches”

Volcanic eruptions on the Moon take place in conditions of low gravity and negligible atmospheric pressure, very different from those on Earth. These differences lead to characteristic lunar versions of hawaiian and strombolian explosive activity, and to the production of unusual eruption products neither predicted nor observed on Earth in the terminal stages of eruptions. These include the unusual mounds and rough (hummocky, blocky) floors of some small-shield summit pit crater floors, elongate depressions and mare flows (similar to those named “irregular mare patches”, IMPs, by Braden et al., 2014). We examine the ascent and eruption of magma in the waning stages of the eruptive process in small-shield summit pit crater floors and show that many IMP characteristics can be plausibly explained by basaltic magma behavior as the rise rate of the ascending magma slows to zero, volatiles exsolve in the dike and lava lake to form a very vesicular foam, and the dike begins to close. Stresses in the very vesicular and porous lava lake crust produce fractures through which the foam extrudes at a rate determined by its non-Newtonian rheology. Waning-stage extrusion of viscous magmatic foams to the surface produces convex mounds whose physical properties inhibit typical impact crater formation and regolith development, creating an artificially young crater retention age. This mechanism for the production and extrusion of very vesicular magmatic foams is also applicable to waning-stage dike closure associated with pit craters atop dikes, and fissure eruptions in the lunar maria, providing an explanation for many irregular mare patches. This mechanism implies that IMPs and associated mare structures (small shields, pit craters and fissure flows) formed synchronously billions of years ago, in contrast to very young ages (less than ~100millionyears) proposed for IMPs by some workers.

INFILTRATION, EFFECTIVE POROSITY, TRANSMISSIBILITY AND CRITICAL YIELD OF WATER WELLS IN THE CARBONATE FISSURED AQUIFERS OF ATTICA – A CONTRIBUTION TO THE REGIONAL AND MANAGERIAL HYDROGEOLOGY

In the hydrogeological practice and the groundwater resources management the accurate knowledge on the infiltration, effective porosity, transmissibility, and on the sustainable yield of water wells is of fundamental value. It is so, because these parameters are the information primarily required in prediction and decisions relevant to the ground water abstractions and the hydrogeological evaluation of specific sites. In this paper, we present these quantities from the carbonate fissured formations of Attica, non metamorphic (limestones, dolomitic limestones, dolomites ) and metamorphic (marbles), which all are of great areal extent and thus of great interest for groundwater exploitation. In addition, they show good geomorphological, structural and lithologic resemblance with analogous formations elsewhere in this country, so that figures calculated can be reliably transferred for use. In our work we used methods of increased reliability, and having known precipitation (P) we estimated — The Infiltration Index (Ic) from the yield of springs of well defined hydrogeological catchments (natural lysimeters) and results found fall in the range of values 0.38P &lt; Ic &lt; 0.42P — The Effective Porosity (pe), obviously secondary because of the nature of the carbonate aquifers ( fissure flow aquifers ). We calculated it from groundwater level hydrograph and values found are in between 1.31%&lt; pe &lt; 6.91% with the most common in between 1.58%&lt; pe &lt; 4.8% — The Transmissibility (T), we calculated from pumping tests, with Jacob method, using semilogarithmic plots of drawdowns (s) versus time (t) from start of pumping. Values found are mostly (70%)in the range 10m3 /h.m &lt; T &lt; 75m3 /h.m — The Critical Yield (Qc) of water wells we calculated from the “characteristic well curve” Q vs. s (with Q and s standing for yield and drawdown respectively). Values are mostly in between 15m3 /h &lt; Qc &lt;75 m3 /h. Cretaceous limestones showed the best of the parameters, followed by the marbles free of schist in- Δελτίο της Ελληνικής Γεωλογικής Εταιρίας, 2010 Bulletin of the Geological Society of Greece, 2010 Πρακτικά 12ου Διεθνούς Συνεδρίου Proceedings of the 12th International Congress Πάτρα, Μάιος 2010 Patras, May, 2010 tercalations and distant from schist boundary . Karstic processes on the fracture network, structures vulnerable to tectonic extension, like anticlines and tension faulting zones are the underlying reasons for better hydrogeologic performance and thus for higher values of the parameters studied. Dolomites outside the previous zones show very low values .