Integration of multiple observed and model-derived hydrological variables in landslide initiation threshold models in Rwanda 

2021 ◽  
Author(s):  
Judith Uwihirwe ◽  
Markus Hrachowitz ◽  
Thom Bogaard
Keyword(s):  
Transfer Function ◽  
Potential Evapotranspiration ◽  
Radial Distance ◽  
Data Availability ◽  
Noise Model ◽  
False Alarms ◽  
Operating Characteristics ◽  
Groundwater Levels ◽  
Linear Reservoir ◽  
Landslide Triggering

<p>This study was conducted using data collected from 3 catchments in North-Western region of Rwanda; Kivu, upper Nyabarongo and Mukungwa. We used two parsimonious  models, a transfer function noise time series model and a linear reservoir conceptual model, to simulate groundwater levels using rainfall and potential evapotranspiration as model inputs. The transfer function noise model was identified as the model with great explanatory predictive power to simulate groundwater levels as compared to the linear reservoir model. Hereafter, the modelled groundwater levels were used together with precipitation to explain the landslide occurrence in the studied catchments. These variables were categorized into landslide predisposing conditions which include the standardized groundwater level on the landslide day h<sub>t</sub> and prior to landslide triggering event h<sub>t-1</sub> and landslide triggering conditions which include the rainfall event, event intensity and duration.  Receiver operating characteristics curve and area under the curve metrics were used to test the discriminatory power of each landslide explanatory variable. The maximum true skill statistics and the minimum radial distance were used to highlight the most informative hydrological and meteorological threshold levels above which landslide are high likely to occur in each catchment. We will discuss our results of incorporation of groundwater information in the landslide predictions and compare these results with landslide prediction capacity which solely use of precipitation thresholds.Here we focus on at the same time on the practicalities of data availability for day-to-day landslide hazard management, both in terms of missed and false alarms</p>

scholarly journals Estimation of groundwater recharge from groundwater levels using nonlinear transfer function noise models and comparison to lysimeter data

2021 ◽  
Vol 25 (5) ◽  
pp. 2931-2949
Author(s):  
Raoul A. Collenteur ◽  
Mark Bakker ◽  
Gernot Klammler ◽  
Steffen Birk
Keyword(s):  
Transfer Function ◽  
Groundwater Recharge ◽  
Nonlinear Model ◽  
Noise Model ◽  
Zone Model ◽  
Research Station ◽  
Parameter Uncertainties ◽  
Groundwater Levels ◽  
Nonlinear Transfer ◽  
Recharge Rates

Abstract. The estimation of groundwater recharge is of paramount importance to assess the sustainability of groundwater use in aquifers around the world. Estimation of the recharge flux, however, remains notoriously difficult. In this study the application of nonlinear transfer function noise (TFN) models using impulse response functions is explored to simulate groundwater levels and estimate groundwater recharge. A nonlinear root zone model that simulates recharge is developed and implemented in a TFN model and is compared to a more commonly used linear recharge model. An additional novel aspect of this study is the use of an autoregressive–moving-average noise model so that the remaining noise fulfills the statistical conditions to reliably estimate parameter uncertainties and compute the confidence intervals of the recharge estimates. The models are calibrated on groundwater-level data observed at the Wagna hydrological research station in the southeastern part of Austria. The nonlinear model improves the simulation of groundwater levels compared to the linear model. The annual recharge rates estimated with the nonlinear model are comparable to the average seepage rates observed with two lysimeters. The recharges estimates from the nonlinear model are also in reasonably good agreement with the lysimeter data at the smaller timescale of recharge per 10 d. This is an improvement over previous studies that used comparable methods but only reported annual recharge rates. The presented framework requires limited input data (precipitation, potential evaporation, and groundwater levels) and can easily be extended to support applications in different hydrogeological settings than those presented here.

scholarly journals The 2010–2015 mega drought in Central Chile: Impacts on regional hydroclimate and vegetation

2017 ◽  
Author(s):  
René Garreaud ◽  
Camila Alvarez-Garreton ◽  
Jonathan Barichivich ◽  
Juan Pablo Boisier ◽  
Duncan Christie ◽  
...  
Keyword(s):  
River Flow ◽  
Potential Evapotranspiration ◽  
Regional Climate ◽  
Climate Scenario ◽  
Annual Rainfall ◽  
Central Chile ◽  
Groundwater Levels ◽  
Tree Ring Reconstruction ◽  
Neutral Conditions ◽  
Northern Sector

Abstract. Since 2010 an uninterrupted sequence of dry years, with annual rainfall deficits ranging from 25 to 45 %, has prevailed in Central Chile (western South America, 30–38° S). Although intense 1- or 2-year droughts are recurrent in this Mediterranean-like region, the ongoing event stands out because of its longevity and large spatial extent. The extraordinary character of the so-called Central Chile Mega Drought (MD) was established against century long historical records and a millennial tree-ring reconstruction of regional precipitation. The largest MD-averaged rainfall relative anomalies occurred in the northern, semi-arid sector of central Chile but the event was unprecedented to the south of 35° S. ENSO neutral conditions have prevailed since 2011 (but for the strong El Niño 2015) contrasting with La Niña conditions that often accompanied past droughts. The precipitation deficit diminished the Andean snowpack and resulted in amplified declines (up to 90 %) of river flow, reservoir volumes and groundwater levels along central Chile and westernmost Argentina. In some semiarid basins we also found a conspicuous decrease in the runoff-to-rainfall coefficient. A substantial decrease in vegetation productivity occurred in the shrubland-dominated, northern sector, but a mix of greening and browning patches occurred farther south where irrigated croplands and exotic forest plantations dominate. The ongoing warming in central Chile, making the MD one of the warmest 6-year period on record, may have also contributed to such complex vegetation changes by increasing potential evapotranspiration. The understanding of the nature and biophysical impacts of the MD contributes to preparedness efforts to face a dry, warm future regional climate scenario.

scholarly journals Landslide precipitation thresholds in Rwanda

Landslides ◽  
2020 ◽  
Vol 17 (10) ◽  
pp. 2469-2481
Author(s):  
Judith Uwihirwe ◽  
Markus Hrachowitz ◽  
Thom A. Bogaard
Keyword(s):  
System Development ◽  
Explanatory Power ◽  
Probabilistic Approach ◽  
Area Under The Curve ◽  
Radial Distance ◽  
Warning System ◽  
High Rate ◽  
Operating Characteristics ◽  
Landslide Occurrence ◽  
Antecedent Precipitation

Abstract Regional empirical-statistical thresholds indicating the precipitation conditions initiating landslides are of crucial importance for landslide early warning system development. The objectives of this research were to use landslide and precipitation data in an empirical-statistical approach to (1) identify precipitation-related variables with the highest explanatory power for landslide occurrence and (2) define both trigger and trigger-cause based thresholds for landslides in Rwanda, Central-East Africa. Receiver operating characteristics (ROC) and area under the curve (AUC) metrics were used to test the suitability of a suite of precipitation-related explanatory variables. A Bayesian probabilistic approach, maximum true skill statistics and the minimum radial distance were used to determine the most informative threshold levels above which landslide are high likely to occur. The results indicated that the event precipitation volumes E, cumulative 1-day rainfall (RD1) that coincide with the day of landslide occurrence and 10-day antecedent precipitation are variables with the highest discriminatory power to distinguish landslide from no landslide conditions. The highest landslide prediction capability in terms of true positive alarms was obtained from single rainfall variables based on trigger-based thresholds. However, that predictive capability was constrained by the high rate of false positive alarms and thus the elevated probability to neglect the contribution of additional causal factors that lead to the occurrence of landslides and which can partly be accounted for by the antecedent precipitation indices. Further combination of different variables into trigger-cause pairs and the use of suitable thresholds in bilinear format improved the prediction capacity of the real trigger-based thresholds.

scholarly journals Process-based modelling to evaluate simulated groundwater levels and frequencies in a Chalk catchment in south-western England

2018 ◽  
Vol 18 (2) ◽  
pp. 445-461 ◽  
Author(s):  
Simon Brenner ◽  
Gemma Coxon ◽  
Nicholas J. K. Howden ◽  
Jim Freer ◽  
Andreas Hartmann
Keyword(s):  
Groundwater Level ◽  
Climate Changes ◽  
Data Availability ◽  
Model Complexity ◽  
High Porosity ◽  
Groundwater Levels ◽  
Subsurface Heterogeneity ◽  
Split Sample ◽  
Sample Test ◽  
Simulated Groundwater

Abstract. Chalk aquifers are an important source of drinking water in the UK. Due to their properties, they are particularly vulnerable to groundwater-related hazards like floods and droughts. Understanding and predicting groundwater levels is therefore important for effective and safe water management. Chalk is known for its high porosity and, due to its dissolvability, exposed to karstification and strong subsurface heterogeneity. To cope with the karstic heterogeneity and limited data availability, specialised modelling approaches are required that balance model complexity and data availability. In this study, we present a novel approach to evaluate simulated groundwater level frequencies derived from a semi-distributed karst model that represents subsurface heterogeneity by distribution functions. Simulated groundwater storages are transferred into groundwater levels using evidence from different observations wells. Using a percentile approach we can assess the number of days exceeding or falling below selected groundwater level percentiles. Firstly, we evaluate the performance of the model when simulating groundwater level time series using a spilt sample test and parameter identifiability analysis. Secondly, we apply a split sample test to the simulated groundwater level percentiles to explore the performance in predicting groundwater level exceedances. We show that the model provides robust simulations of discharge and groundwater levels at three observation wells at a test site in a chalk-dominated catchment in south-western England. The second split sample test also indicates that the percentile approach is able to reliably predict groundwater level exceedances across all considered timescales up to their 75th percentile. However, when looking at the 90th percentile, it only provides acceptable predictions for long time periods and it fails when the 95th percentile of groundwater exceedance levels is considered. By modifying the historic forcings of our model according to expected future climate changes, we create simple climate scenarios and we show that the projected climate changes may lead to generally lower groundwater levels and a reduction of exceedances of high groundwater level percentiles.

scholarly journals Catchment-scale non-linear groundwater-surface water interactions in densely drained lowland catchments

2009 ◽  
Vol 13 (10) ◽  
pp. 1867-1885 ◽  
Author(s):  
Y. van der Velde ◽  
G. H. de Rooij ◽  
P. J. J. F. Torfs
Keyword(s):  
Surface Water ◽  
Distributed Hydrological Model ◽  
Catchment Scale ◽  
Channel Network ◽  
Groundwater Levels ◽  
Travel Time Distribution ◽  
Spatially Distributed ◽  
Linear Reservoir ◽  
Active Channel ◽  
Model Approach

Abstract. Freely discharging lowland catchments are characterized by a strongly seasonal contracting and expanding system of discharging streams and ditches. Due to this rapidly changing active channel network, discharge and solute transport cannot be modeled by a single characteristic travel path, travel time distribution, unit hydrograph, or linear reservoir. We propose a systematic spatial averaging approach to derive catchment-scale storage and discharge from point-scale water balances. The effects of spatial heterogeneity in soil properties, vegetation, and drainage network are lumped and described by a relation between groundwater storage and the spatial probability distribution of groundwater depths with measurable parameters. The model describes how, in lowland catchments, the catchment-scale flux from groundwater to surface water via various flow routes is affected by a changing active channel network, the unsaturated zone and surface ponding. We used observations of groundwater levels and catchment discharge of a 6.6 km2 Dutch watershed in combination with a high-resolution spatially distributed hydrological model to test the model approach. Good results were obtained when modeling hourly discharges for a period of eight years. The validity of the underlying assumptions still needs to be tested under different conditions and for catchments of various sizes. Nevertheless, at this stage the model can already improve monitoring efficiency of groundwater-surface water interactions.

scholarly journals Estimating groundwater recharge from groundwater levels using non-linear transfer function noise models and comparison to lysimeter data

2020 ◽  
Author(s):  
Raoul Collenteur ◽  
Mark Bakker ◽  
Gernot Klammler ◽  
Steffen Birk
Keyword(s):  
Transfer Function ◽  
Groundwater Recharge ◽  
Linear Model ◽  
Zone Model ◽  
Research Station ◽  
Parameter Uncertainties ◽  
Groundwater Levels ◽  
Linear Transfer Function ◽  
Non Linear ◽  
Recharge Rates

Abstract. The application of non-linear transfer function noise (TFN) models using impulse response functions is explored to estimate groundwater recharge and simulate groundwater levels. A non-linear root zone model that simulates recharge is developed and implemented in a TFN model, and is compared to a more commonly used linear recharge model. An additional novel aspect of this study is the use of an autoregressive-moving average noise model so that the remaining noise fulfills the statistical conditions to reliably estimate parameter uncertainties and compute the confidence intervals of the recharge estimates. The models are calibrated on groundwater level data observed at the Wagna hydrological research station in the southeastern part of Austria. The non-linear model improves the simulation of groundwater levels compared to the linear model. The annual recharge rates estimated with the non-linear model are comparable to the average seepage rates observed with two lysimeters. The recharges estimates from the non-linear model are also in reasonably good agreement with the lysimeter data at the smaller time scale of recharge per 10 days. This is an improvement over the results from previous studies that used comparable methods, but only reported annual recharge rates. The presented framework requires limited input data (precipitation, potential evaporation, and groundwater levels) and can easily be extended to support applications in different hydrogeological settings than those presented here.

scholarly journals Potential of Shallow Groundwater for Household Level Irrigation Practices in Tahtay Koraro Woreda, Tigray, Northern Ethiopia

2021 ◽  
Vol 13 (1) ◽  
pp. 43-66
Author(s):  
Ermias Hagos ◽  
Amare Girmay ◽  
Tesfamichael Gebreyohannes
Keyword(s):  
Groundwater Recharge ◽  
Large Scale ◽  
Potential Evapotranspiration ◽  
Shallow Groundwater ◽  
Northern Ethiopia ◽  
Groundwater Abstraction ◽  
Groundwater Levels ◽  
Household Level ◽  
Average Value ◽  
Dug Wells

This paper deals with the results of a pilot study conducted to estimate the shallow groundwater resource potential and irrigation capacity at the household level in Tahtay Koraro Woreda, northwestern zone of Tigray, Ethiopia. The potential evapotranspiration and actual evapotranspiration of the study area are estimated to be 1484 mm/year and 814 mm/year respectively. The runoff is approximately calculated to be 280 mm/year and the annual groundwater recharge is estimated to be 29 mm/year. The total annual groundwater abstraction for human, livestock, and irrigation is estimated to be 25 mm/year. It should be noted that the groundwater recharge rate is expected to remain constant while the total annual groundwater discharge is expected to increase from year to year. This relation when projected over a long period may result in a negative groundwater budget which can result in depletion of groundwater (lowering of groundwater levels), reduced baseflow to streams, and deterioration of water quality.  The computed values for hydraulic conductivity of the aquifers range from 1.63 m/day to 7.27 m/day with an average value of 4.9 m/day and transmissivity from 48.9 m2/day to 218.1 m2/day with an average value of 147.14 m2/day. The aquifers in the highly weathered basalt and highly weathered siltstone – sandstone intercalation have transmissivity values ranging from 99 m2/day to 218.1 m2/day with an average value of 157 m2/day and are grouped into the moderate potentiality aquifers category. The aquifers in the slightly weathered and fractured metavolcanics grouped under low potentiality based on the lower transmissivity values (<50 m2/day). The study area has low to moderate groundwater potentiality, hence, large-scale groundwater pumping is not possible. Therefore, the current activity of using hand dug wells for household-level irrigation is the best way of using groundwater for irrigation and other uses as well. Increasing the depth of the existing hand dug wells that are constructed in highly weathered basalt and highly weathered siltstone – sandstone intercalation can also enhance the yield of the hand dug wells. It is recommended to use water-saving irrigation technologies rather than increasing the number of wells. This will also help in increasing the irrigation area. Groundwater recharge enhancement structures such as trenches, percolation ponds, and check dams be constructed in scientifically selected localities to further enhance the groundwater potential.

scholarly journals A percentile approach to evaluate simulated groundwater levels and frequencies in a Chalk catchment in Southwest England

2016 ◽  
Author(s):  
Simon Brenner ◽  
Gemma Coxon ◽  
Nicholas J. K. Howden ◽  
Jim Freer ◽  
Andreas Hartmann
Keyword(s):  
Groundwater Level ◽  
Climate Changes ◽  
Data Availability ◽  
Model Complexity ◽  
High Porosity ◽  
Groundwater Levels ◽  
Subsurface Heterogeneity ◽  
Split Sample ◽  
Sample Test ◽  
Simulated Groundwater

Abstract. Chalk aquifers are an important source of drinking water in the UK. Understanding and predicting groundwater levels is therefore important for effective water management of this resource. Chalk is known for its high porosity and, due to its dissolvability, exposed to karstification and strong subsurface heterogeneity. To cope with the karstic heterogeneity and limited data availability, specialised modelling approaches are required that balance model complexity and data availability. In this study we present a novel approach to simulate groundwater level frequency distributions with a semi-distributed karst model that represents subsurface heterogeneity by distribution functions. Simulated groundwater storages are transferred into groundwater levels using evidence from different observations wells. Using a newly developed percentile approach we can simulate the number of days exceeding or falling below selected groundwater level percentiles. Firstly, we evaluate the performance of the model to simulate three groundwater time series by a spilt sample test and parameter identifiability analysis. Secondly, we apply a split sample test on the simulated groundwater level percentiles to explore the performance in predicting groundwater level exceedances. We show that the model provides robust simulations of discharge and groundwater levels at 3 observation wells at a test site in chalk dominated catchment in Southwest England. The second split sample test also indicates that percentile approach is able to reliably predict groundwater level exceedances across all considered time scales up to their 75th percentile. However, when looking at the 90th percentile, it only provides acceptable predictions for the longest available time scale and it fails when the 95th percentile of groundwater exceedance levels is considered. Modifying the historic forcings of our model according to expected future climate changes, we create simple climate scenarios and we show that the projected climate changes may lead to generally lower groundwater levels and a reduction of exceedances of high groundwater level percentiles.

scholarly journals Temporal dependence of potentiometric levels and groundwater salinity in alluvial aquifer upon rainfall and evapotranspiration

RBRH ◽  
2017 ◽  
Vol 22 (0) ◽  
Author(s):  
Robertson Valério de Paiva Fontes Júnior ◽  
Abelardo Antônio de Assunção Montenegro
Keyword(s):  
Temporal Dynamics ◽  
Potential Evapotranspiration ◽  
Shallow Groundwater ◽  
Temporal Analysis ◽  
Alluvial Aquifer ◽  
Monthly Precipitation ◽  
Groundwater Salinity ◽  
Temporal Dependence ◽  
Time Pattern ◽  
Groundwater Levels

ABSTRACT Rainfall uncertainty and high evapotranspiration rates in the semiarid regions not only play an important impact on surface water scarcity, but interfere on shallow groundwater quantity and quality. The aim of this study was to apply geostatistical methodology to analyze the time dependence of potentiometric levels and groundwater salinity in an intensively monitored alluvial aquifer upon agroclimatological variables, and thus investigate possible monthly and annual correlations. Statistically stable piezometers were considered for the temporal analysis, representing the mean behavior of the whole aquifer. It has been verified that stable piezometers for groundwater levels exhibited temporal dependence of 7 months, similar to the temporal scale of variation for monthly precipitation and potential evapotranspiration, which is consistent to the resulting crossed-semivariogram. Meanwhile, stable piezometers for electrical conductivity showed high uncertainty on temporal dependence scale, which ranged from 3 to 8 months. Thus, rainfall and evapotranspiration alone did not properly explain the temporal dynamics of groundwater salinity. The produced maps successfully identified the long term time pattern of groundwater variation, constituting an important support for water resources evaluation.

scholarly journals Is U.S. Multinational Dividend Repatriation Policy Influenced by Reporting Incentives?

2012 ◽  
Vol 87 (5) ◽  
pp. 1463-1491 ◽  
Author(s):  
Jennifer L. Blouin ◽  
Linda K. Krull ◽  
Leslie A. Robinson
Keyword(s):  
Multinational Corporations ◽  
Financial Reporting ◽  
Data Availability ◽  
Operating Characteristics ◽  
Foreign Earnings ◽  
Reporting Incentives ◽  
Cash Payment ◽  
Public Company ◽  
Foreign Affiliates ◽  
Repatriation Taxes

ABSTRACT This study finds evidence that public-company reporting by U.S. multinational corporations (MNCs) creates disincentives to repatriate foreign earnings to the U.S. and contributes to the accumulation of cash abroad. MNCs operate under U.S. international tax laws and financial reporting rules and face two potential consequences when they repatriate foreign earnings: a cash payment for repatriation taxes and a reduction in reported accounting earnings. Using a confidential dataset of financial and operating characteristics of foreign affiliates of MNCs combined with public-company data, we examine how repatriation amounts vary across firms that face relatively strong reporting incentives to defer an accounting expense. Our results suggest that reporting incentives reduce repatriations by about 17 to 21 percent annually. Data Availability: Bureau of Economic Analysis (BEA) data were made available to the authors under a legal confidentiality arrangement; all non-BEA data are available from public sources.

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