Eden Valley observation boreholes : hydrogeological framework and groundwater level time series analysis

This report summarises the analysis of groundwater level data from 26 boreholes in the Eden Valley, Cumbria. By undertaking a statistical analysis on 18 of these boreholes greater insight into the hydrogeology has been obtained. The work is presented to build a foundation on which greater analysis can be undertaken

Use of seasonal trend decomposition to understand groundwater behaviour in the Permo-Triassic Sandstone aquifer, Eden Valley, UK

The daily groundwater level (GWL) response in the Permo-Triassic Sandstone aquifers in the Eden Valley, England (UK), has been studied using the seasonal trend decomposition by LOESS (STL) technique. The hydrographs from 18 boreholes in the Permo-Triassic Sandstone were decomposed into three components: seasonality, general trend and remainder. The decomposition was analysed first visually, then using tools involving a variance ratio, time-series hierarchical clustering and correlation analysis. Differences and similarities in decomposition pattern were explained using the physical and hydrogeological information associated with each borehole. The Penrith Sandstone exhibits vertical and horizontal heterogeneity, whereas the more homogeneous St Bees Sandstone groundwater hydrographs characterize a well-identified seasonality; however, exceptions can be identified. A stronger trend component is obtained in the silicified parts of the northern Penrith Sandstone, while the southern Penrith, containing Brockram (breccias) Formation, shows a greater relative variability of the seasonal component. Other boreholes drilled as shallow/deep pairs show differences in responses, revealing the potential vertical heterogeneities within the Penrith Sandstone. The differences in bedrock characteristics between and within the Penrith and St Bees Sandstone formations appear to influence the GWL response. The de-seasonalized and de-trended GWL time series were then used to characterize the response, for example in terms of memory effect (autocorrelation analysis). By applying the STL method, it is possible to analyse GWL hydrographs leading to better conceptual understanding of the groundwater flow. Thus, variation in groundwater response can be used to gain insight into the aquifer physical properties and understand differences in groundwater behaviour

Malawi Hydrogeological and Water Quality Mapping: Assessing Groundwater Resources Under Extreme Weather

The distributed recharge model developed by Scheidegger et al. (2015) is used to estimate the recharge values under extreme weather events. Synthetic extreme dry and wet rainfall and evaporation time series are produced by repeating a dry or a wet year within the historical rainfall and evaporation time series. The Standardised Precipitation Index (SPI) method is used to identify the most wet and most dry years. Heat maps showing the severity of drought or wet periods across the country are used. These maps show inconsistencies of the calculated indices across the country, with oddities observed in the north part of the country. Six scenarios are considered in which, the wet year is repeated once, twice, and three times and then the dry year is repeated in the same fashion. The estimated long term average recharge values are compared to the historical ones. On average, the groundwater system is expected to be in shortage of 9% of historical long term average recharge values calculated for the country when four successive years of drought years are considered. The groundwater system contains approximately 11 % more resources than that is calculated historically when four successive wet years are considered. AquiMod lumped groundwater model is used to estimate representative transmissivity and storage coefficient values for three catchments. Groundwater levels recorded at the boreholes in Chitipa, Endongolweni School, and Namwera are used for this purpose. The numerical model produces acceptable groundwater time series for the first two boreholes but fails to produce the groundwater level fluctuations at the Namwera borehole. It is believed that inconsistencies between the calculated recharge and the groundwater level time series are the reason for this failure. The optimised hydrogeological parameters lead to transmissivity values varied between 20 and 1500 m2/day. Storage coefficient (specific yield) on the other hand varied between 0.02 and 0.3. The AquiMod models were run using the synthetic meteorological extreme scenarios and the groundwater level fluctuations are compared to those produced using the historical recharge values. The uncertainties associated with the determination of extreme weather periods in the northern Malawi are propagated in this modelling exercise. Whereas the higher extreme weather signals in the south lead to the determination of clearly identifiable extreme weather events, the less clear signals in the north induce the production of incorrect synthetic wet scenarios for this region

Malawi Hydrogeological and Water Quality Mapping: National Scale Recharge Estimation

A toolbox of different recharge values and a distributed recharge model have been applied to estimate the recharge values over Malawi. The toolbox is prepared within Microsoft Excel and coded using Visual Basics. The distributed recharge calculation is undertaken using the BGS ZOODRM model. The model uses gridded daily rainfall and potential evaporation data as well as gridded landuse, topography, soil, and river data to calculate recharge. The distributed recharge model is calibrated by matching the simulated overland flows to the observed ones at selected gauging stations. However, difficulties were encountered during the calibration of the recharge model due to: (i) the resolution of the model grid being relatively coarse so that the topographical characteristics could not be fully captured, (ii) the number of runoff zones specified in the model not being enough to represent the characteristics of the study area, and (iii) there being a need to improve the representation of land cover in the model since the land cover affects the estimated recharge values. The estimated recharge values presented in this study are highly affected by the quality of data used in the distributed recharge model. Comparing the recharge values estimated from the recharge model and averaged over the district areas to the recharge values calculated using the recharge toolbox, it was clear that the former agree with the values of at least one analytical method included in the toolbox. However, there was no consistency of agreement, i.e. the recharge values produced by the distributed model did not agree with one particular method. The sensitivity analysis results indicate that the recharge values are highly affected by the soil type parameter values specified in the model and by the definition of spatial distribution of land cover. To improve the accuracy of recharge calculations using the distributed recharge model, it is recommended that maps with a better representation of these features are included in the model. In addition, further model calibration runs are needed to improve the quality of the estimated recharge values. This can be only achieved by obtaining better field data

KOMPOSISI JENIS TUMBUHAN HERBA PADA HUTAN PEGUNUNGAN DI SEKITAR DANAU KALIMPA’A KAWASAN TAMAN NASIONAL LORE LINDU SULAWESI TENGAH

The research entitled “Composition of Herbs Plant Species in The Mountain Forest  Around the Kalimpa'a Lake Lore Lindu National Park Central Sulawesi” was conducted in April to June 2016. This research aims is to study and to determine the species composition of herbaceous plants that grow in the mountain forest around Kalimpa’a Lake Lore Lindu National Park area. The environmental factors such  as;  air temperature, humidity and light intensity were measured by Thermohygrometer and Lux meter.  GPS was used to measure the position geography and altitude. The data of  rainfall was obtained from the Meteorological, Climatological and Geophysics Mutiara Sis Al-Djufire Airport Palu. The research carried out in a survey with using single plot method with 50 x 50 m in size. In this  plot was subdivided into 25 subplots of 2 x 2 m² (recording units) to observe herbs diversity. The resut of the reseach showed that  there were twenty six (26) species, consist of  twenty five (25) genera and nineteen (19) families herbs plant species with the number of individuals 469. The dominant species of was Borreria alata (Aubl.) DC. with Important Value (IV) of 32,06%. It followed by  Alpinia sp and Goodyera celebica  with IV  23.73% and 21,23% respectively. Meanwhile, the lowest of Important Value (1,21%) was Genarium potentilloides. The species diversity index (H’) in this research was chategorized to medium with H’ = 2.73. Of the 26 species of herbaceous plants founded, a number of them were endemic to Sulawesi namely; Goodyera celebica Blume, Alyxia celebica D.G.Middlleton and Freycenetia minahassae Koord

Use of point scale models to improve conceptual understanding in complex aquifers: an example from a sandstone aquifer in the Eden valley, Cumbria, UK

Understanding catchment functioning is increasingly important to enable water resources to be quantified and used sustainably, flood risk to be minimized, as well as to protect the system from degradation by pollution. Developing conceptual understanding of groundwater systems and their encapsulation in models is an important part of this understanding, but they are resource intensive to create and calibrate. The relative lack of data or the particular complexity of a groundwater system can prevent the development of a satisfactory conceptual understanding of the hydrological behaviour, which can be used to construct an adequate distributed model. A time series of daily groundwater levels from the Permo-Triassic sandstones situated in the River Eden Valley, Cumbria, UK have been analysed. These hydrographs show a range of behaviours and therefore have previously been studied using statistical and time series analysis techniques. This paper describes the application of AquiMOD, impulse response function (IRF) and combined AquiMOD-IRF methods to characterize the daily groundwater hydrographs. The best approach for each characteristic type of response has been determined and related to the geological and hydrogeological framework found at each borehole location. It is clear that AquiMOD, IRF and a combination of AquiMOD with IRF can be deployed to reproduce hydrograph responses in a range of hydrogeological settings. Importantly the choice of different techniques demonstrates the influence of differing processes and hydrogeological settings. Further they can distinguish the influences of differing hydrogeological environments and the impacts these have on the groundwater flow processes. They can be used, as shown in this paper, in a staged approach to help develop reliable and comprehensive conceptual models of groundwater flow. This can then be used as a solid basis for the development of distributed models, particularly as the latter are resource expensive to build and to calibrate effectively. This approach of using simple models and techniques first identifies specific aspects of catchment functioning, for example influence of the river, that can be later tested in a distributed model

Mathematical modeling of karstogenesis: an approach based on fracturing and hydrogeological processes

The karstogenesis of a synthetic aquifer is analyzed as a function of the matrix permeability and the fracture density affecting the carbonate reservoir. The synthetic carbonate aquifer generation results from numerical simulations based on Discrete Fracture Network (DFN) and groundwater flow simulations. The aim is to simulate karstogenesis processes in an aquifer characterized by a fracture network, while matching field reality and respecting geometrical properties as closely as possible. DFN are simulated with the soft REZO3D that allows the generation of 3-D realistic fracture networks, especially regarding the relative position of fractures that control the overall network connectivity. These generated DFN are then meshed and considered to perform groundwater flow simulation with the model GroundWater (GW). At each time step and for each fracture element, flow velocity and the mean groundwater age are extracted and used in an analogical dissolution equation that computes the aperture evolution. This equation relies on empirical parameters calibrated with former speleogenesis studies. In this paper, karstogenesis simulations are performed using fixed-head hydraulic boundary conditions within a single stratum as a function of two fracture density settings. The results are interpreted in terms of head fields, mean groundwater age distributions; while total flow rate and average aperture are analyzed as a function of time. The effect of fracture density and rock matrix permeability are then assessed

Flash flood mitigation as a positive consequence of anthropogenic forcing on the groundwater resource in a karst catchment

The Mediterranean coastal region is prone to high-intensity rainfall events that are frequently associated with devastating flash floods. This paper discusses the role of a karst aquifer system in the flash floods of a Mediterranean river, the Lez river. Most of the Lez river watershed is located on karst terrains where interactions between surface water and groundwater take place. During extreme rainfall events, the presence of fractures and well-developed karst features in carbonate terrains enhances the infiltration processes and involves the concentration of the recharge into highly organized and permeable flow paths. The groundwater, therefore, quickly moves towards the natural outlets of the karst system. The influence of the Lez karst aquifer system on the associated river floods dynamics is analysed while considering the spatially distributed rainfall, as well as the time series of the groundwater level within the aquifer and of the Lez river discharge measured at various gauging stations. Special attention is given to the relative importance of the surface and underground processes involved in flash flood genesis. It is shown that the karst groundwater contributes to flash floods under certain conditions, while high-rate pumping within the karst aquifer, which generates significant drawdown, may mitigate flash floods under other conditions

Modélisation mathématique de la spéléogenèse : une approche hybride à partir de réseaux de fractures discrets et de simulations hydrogéologiques

The main objective of this thesis is to provide an approach ofspeleogenesis modeling which would allow to bring new knowledge on the genesis of the Mediterranean karstic systems.Several numerical modeling approaches of speleogenesis exist. They take intoaccount physical and chemical laws for flow and dissolution in fractured carbonate aquifers. Nevertheless, the initial void networks considered by these models gene-rally do not correspond to the fracturing reality.The proposed approach aims to simulate karstogenesis in an aquifer characterizedby a fracture network, while matching field reality as closely as possible andrespecting geometrical properties. Using statistical and geometrical parameters obtained by field observations and analogical experiments, it is possible to generate3-D realistic networks in terms of the relative position of joints that control theoverall network connectivity.Once the fracture networks are generated, they are adapted and incorporated in a3-D ground water flow and transport finite element model. The flow simulationsin the fracture networks allow the determination of the spatial distribution of porevelocities for the initial configuration. This distribution, added to the distributedage of the groundwater, is used to simulate the evolution of the aperture of the different elements by the use of a dedicated empirical equation.The calibration of the empirical growth law is carried out considering initial testson single fractures, taking previous works as reference, and leading sensitivity analyses. Results of simulations taking into account a limestone matrix surrounding the conduit, and considering various values of hydraulic conductivity of the matrixand various recharge conditions, are presented.Then, results obtained considering configurations designed with a single stratum containing fracture networks are presented, considering various fracture densities,matrix hydraulic conductivities and boundary conditions.L'objectif principal de cette thèse est de proposer une nouvelle approche de modélisation de la spéléogenèse, susceptible à terme d'acquérir de nouvelles connaissances concernant la mise en place des systèmes karstiques méditerranéens.Il existe plusieurs approches de modélisations numériques de la spéléogenèse,prenant en compte des lois physiques et chimiques contrôlant l'écoulement et la dissolution au sein des aquifères fracturés carbonatés. Néanmoins, les réseaux de vides initiaux considérés par ces modèles ne correspondent en général pas à la réalité de la fracturation.L'approche proposée vise à simuler la karstogenèse au sein d'un aquifère caractérisé par un réseau fracturé, aussi réaliste que possible et satisfaisant des propriétés géométriques.Prenant en compte des paramètres statistiques et géométriques pouvant être obtenus par des observations sur le terrain et des expériences analogiques, il est possible de générer des réseaux 3-D réaliste en termes de position relative des diaclases, qui contrôlé la connectivité globale du réseau.Une fois les réseaux de fractures générés, ceux-ci sont traités afin de construire un maillage incorporé dans un modèle à éléments finis d'écoulement et de transport des eaux souterraines. Les simulations d'écoulement et de transport au sein des réseaux fracturés permettent de déterminer la distribution des vitesses d'écoulement ainsi que de l'âge de l'eau souterraines. Ces distributions sont utilisées pour simuler l'évolution de l'ouverture des différents éléments au moyen de l'application d'une loi empirique dédiée de forme polynomiale.Le calibrage de cette loi est effectué au moyen de tests de type benchmark portant sur des configurations de fracture unique, prenant pour référence des travaux existants, et réalisant des analyses de sensibilité. Des résultats de simulations prenant en compte une matrice carbonatée incorporant la fracture ou le conduit unique, et considérant différentes valeurs de perméabilité matricielle et différentes modalités de recharge, sont présentés. Enfin, des résultats obtenus considérant des configurations caractérisées par une strate carbonatée contenant des réseaux de fractures sont présentés, considérant différentes densités de fracturation, conductivités hydrauliques matricielles et conditions aux limites