Publications

@article{KISI2024102017,

title = {Enhancing river flow predictions: Comparative analysis of machine learning approaches in modeling stage-discharge relationship},

author = {Ozgur Kisi and Hazi Mohammad Azamathulla and Fatih Cevat and Christoph Kulls and Mehdi Kuhdaragh and Mehdi Fuladipanah},

url = {https://www.sciencedirect.com/science/article/pii/S2590123024002706},

doi = {https://doi.org/10.1016/j.rineng.2024.102017},

issn = {2590-1230},

year  = {2024},

date = {2024-01-01},

journal = {Results in Engineering},

volume = {22},

pages = {102017},

abstract = {Streamflow, a pivotal variable in water resources management, holds profound significance in shaping the decision-making processes of hydrologic projects. This paper tries to delve into the exploration of the stage-discharge relationship using three machine learning methods (MLMs) namely multi-layer neural networks (MLNN), radial basis neural networks (RBNN), and neuro-fuzzy systems (ANFIS) to predict and simulate mean daily stage-discharge data derived from two monitoring stations, Bulakbasi and Karaoz\~{A}¼, Kizilirmak River, Turkey. Root mean square error (RMSE), Mean absolute percentage error (MAPE), coefficient of determination (R2), and the Developed Discrepancy Ratio (DDR) metrics were utilized to MLMs' performance assessment. The performance evaluation indices (RMSE, MAEP, R2, DDR) for the preeminent MLNN model applied to Bulakhbashi and Karasu stations were determined as (0.29, 1.57, 0.9998, 17.62) and (1.71, 6.56, 0.9980, 6.65), respectively. The MLNN model contributed to a notable enhancement in the RMSE performance index for the aforementioned stations, exhibiting improvements of 87% and 56%, respectively. These results affirm the MLNN's proficiency in accurately capturing the stage-discharge at both monitoring stations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{OLA2024101405,

title = {Remediating Oil Contamination in the Niger Delta Region of Nigeria: Technical Options and Monitoring Strategies},

author = {Ibukun Ola and Carsten Drebenstedt and Robert M. Burgess and Martin Mensah and Nils Hoth and Christoph K\~{A}¼lls},

url = {https://www.sciencedirect.com/science/article/pii/S2214790X24000030},

doi = {https://doi.org/10.1016/j.exis.2024.101405},

issn = {2214-790X},

year  = {2024},

date = {2024-01-01},

journal = {The Extractive Industries and Society},

volume = {17},

pages = {101405},

abstract = {The Niger Delta, a region of immense ecological significance and rich biodiversity, has long faced the severe consequences of petroleum contamination resulting from intense oil exploration and various environmental stressors. In response to the pressing need for effective remediation and monitoring of contaminated matrices in the Niger Delta, this study delves into a comprehensive analysis. Through a systematic assessment considering certain criteria, advanced remediation technologies tailored to the specific environmental challenges in the region are identified. Organoclay-based reactive core materials (RCM), permeable reactive barriers (PRBs), and bioremediation have emerged as highly suitable solutions for remediating sediment, groundwater, and soil, respectively. These technologies span the spectrum from non-intrusive to less intrusive methods and have demonstrated exceptional efficacy in mitigating hydrocarbon contamination under the delta's prevailing complex conditions. In addressing the critical need for monitoring the progress of remediation and post-remediation stages, a fully integrated approach is proposed. This strategy combines three essential components for tracking environmental quality improvements and understanding the recovery processes: traditional total chemical concentration (Ctotal) estimates, passive sampler-derived freely dissolved chemical concentration (Cfree) measurements, and ecological monitoring, specifically the recolonization test. Together, these components provide a more accurate description of risk and a comprehensive understanding of the recovery process. This study is concentrated on the systematic selection, supported by credible case study information, of tailored technical solutions for addressing the unique challenges of the Niger Delta. The novel outcomes lie in the identification of technology solutions carefully adapted for the region, representing a significant advancement in the field of environmental remediation in the Niger Delta. Science-based remediation and monitoring are key, and this study offers a decision support tool for selecting optimal methods in the ongoing cleanup of the Niger Delta and similar areas. This supports a healthier, more resilient environment for both the region's inhabitants and ecosystems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Eliades2022,

title = {Quantifying Evapotranspiration and Drainage Losses in a Semi-Arid Nectarine (Prunus persica var. nucipersica) Field with a Dynamic Crop Coefficient (Kc) Derived from Leaf Area Index Measurements},

author = {M. Eliades and A. Bruggeman and H. Djuma and C. Christofi and C. Kuells},

doi = {10.3390/w14050734},

issn = {2073-4441},

year  = {2022},

date = {2022-01-01},

journal = {Water},

volume = {14},

number = {5},

abstract = {Quantifying evapotranspiration and drainage losses is essential for improving irrigation efficiency. The FAO-56 is the most popular method for computing crop evapotranspiration. There is, however, a need for locally derived crop coefficients (Kc) with a high temporal resolution to reduce errors in the water balance. The aim of this paper is to introduce a dynamic Kc approach, based on Leaf Area Index (LAI) observations, for improving water balance computations. Soil moisture and meteorological data were collected in a terraced nectarine (Prunus persica var. nucipersica) orchard in Cyprus, from 22 March 2019 to 18 November 2021. The Kc was derived as a function of the canopy cover fraction (c), from biweekly in situ LAI measurements. The use of a dynamic Kc resulted in Kc estimates with a bias of 17 mm and a mean absolute error of 0.8 mm. Evapotranspiration (ET) ranged from 41% of the rainfall (P) and irrigation (I) in the wet year (2019) to 57% of P + I in the dry year (2021). Drainage losses from irrigation (DR_I) were 44% of the total irrigation. The irrigation efficiency in the nectarine field could be improved by reducing irrigation amounts and increasing the irrigation frequency. Future studies should focus on improving the dynamic Kc approach by linking LAI field observations with remote sensing observations and by adding ground cover observations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Christofi2020hydrochemical,

title = {Hydrochemical evolution of groundwater in gabbro of the Troodos Fractured Aquifer. A comprehensive approach},

author = {C. Christofi and A. Bruggeman and C. K\"{u}lls and C. Constantinou},

doi = {https://doi.org/10.1016/j.apgeochem.2020.104524},

year  = {2020},

date = {2020-01-01},

journal = {Applied Geochemistry},

volume = {114},

pages = {104524},

publisher = {Pergamon},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Christofi2020104780,

title = {Isotope hydrology and hydrogeochemical modeling of Troodos Fractured Aquifer, Cyprus: The development of hydrogeological descriptions of observed water types},

author = {C. Christofi and A. Bruggeman and C. K\"{u}lls and C. Constantinou},

issn = {0883-2927},

year  = {2020},

date = {2020-01-01},

journal = {Applied Geochemistry},

volume = {123},

pages = {104780},

abstract = {The origin of groundwater recharge and subsequent flow paths are often difficult to establish in fractured, multi-lithological, and highly compartmentalized aquifers such as the Troodos Fractured Aquifer (TFA). As the conjunctive use of stable isotopes and hydrogeochemical data provides additional information, we established a monitoring network for stable isotopes in precipitation in Cyprus. The local meteoric water line, altitude effect and seasonal variation of stable isotopes in precipitation are derived from monitoring data. Stable isotopes and hydrogeochemical data are combined to model water-rock interactions and groundwater evolution along a complete ophiolite sequence. As a result a generic hydrogeologic description for the observed water types is developed. Isotope hydrology was applied in conjunction with hydrogeochemical modelling in Kargiotis Watershed, a major north-south transect of the TFA. PHREEQC was used for hydrogeochemical modelling to establish generic descriptions for observed water types. Mean precipitation-weighted values from 16 monitoring stations were used to calculate the Local Meteoric Water Line (LMWL), which was found to be equal to δ2H = (6.58~±~0.13)*δ18O~+~(12.64~±~0.91). A general decrease of 1.22texttenthousand for δ2H and 0.20texttenthousand for δ18O in precipitation was calculated per 100~m altitude. A generic groundwater evolution path was established: 1. Na/MgClHCO3, 2. MgHCO3, 3. Ca/MgHCO3, 4. Ca/MgNaHCO3, 4a. MgNa/CaHCO3/Cl, 5. NaMg/CaHCO3/Cl, 6. NaHCO3, 7. Na/MgHCO3SO4, 8. NaSO4Cl/HCO3. Hydrogeologic descriptions, consisting of groundwater origin, flow path and possible active water-rock processes, have been realised for the observed water types. The first two water types occur in serpentine and ultramafic-gabbro springs. Type 3 waters represent early stages of recharge and/or short flow paths, in gabbro whereas types 4 and 5 are typical for further percolating waters in gabbro and diabase. Water types 6 and 7 occur both in diabase and in the basal group and represent the regional flow. Water type 8 is the end member of regional, upwelling groundwater in the basal group. The presented descriptions and methods have practical applications in groundwater exploration, characterization, and protection. The methodology can be applied in other complex aquifer systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mahindawansha2020investigating,

title = {Investigating unproductive water losses from irrigated agricultural crops in the humid tropics through analyses of stable isotopes of water},

author = {A. Mahindawansha and C. K\"{u}lls and P. Kraft and L. Breuer},

doi = {https://doi.org/10.5194/hess-24-3627-2020},

year  = {2020},

date = {2020-01-01},

journal = {Hydrology and Earth System Sciences},

volume = {24},

number = {7},

pages = {3627\textendash3642},

publisher = {Copernicus GmbH},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Joseph2019application,

title = {Application of a laser-based spectrometer for continuous in situ measurements of stable isotopes of soil CO2 in calcareous and acidic soils},

author = {J. Joseph and C. K\"{u}lls and M. Arend and M. Schaub and F. Hagedorn and A. Gessler and M. Weiler},

doi = {https://doi.org/10.5194/soil-5-49-2019},

year  = {2019},

date = {2019-01-01},

journal = {Soil},

volume = {5},

number = {1},

pages = {49\textendash62},

publisher = {Copernicus},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hamutoko2014fingerprinting,

title = {A fingerprinting method for the identification of uranium sources in alluvial aquifers: An example from the Khan and Swakop Rivers, Namibia},

author = {J. Hamutoko and B. Mapani and R. Ellmies and A. Bittner and C. K\"{u}lls},

year  = {2014},

date = {2014-01-01},

journal = {Physics and Chemistry of the Earth, Parts A/B/C},

volume = {72},

pages = {34\textendash42},

publisher = {Pergamon},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mueller2014tracking,

title = {Tracking water pathways in steep hillslopes by δ18O depth profiles of soil water},

author = {M. M\"{u}ller and A. Alaoui and C. K\"{u}lls and H. Leistert and K. Meusburger and C. Stumpp and M. Weiler and C. Alewell},

doi = {https://doi.org/10.1016/j.jhydrol.2014.07.031},

year  = {2014},

date = {2014-01-01},

journal = {Journal of hydrology},

volume = {519},

pages = {340\textendash352},

publisher = {Elsevier},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Baram2013desiccation,

title = {Desiccation-crack-induced salinization in deep clay sediment},

author = {S. Baram and Z. Ronen and D. Kurtzman and C. K\"{u}lls and O. Dahan},

doi = {https://doi.org/10.5194/hess-17-1533-2013},

year  = {2013},

date = {2013-01-01},

journal = {Hydrology and Earth System Sciences},

volume = {17},

number = {4},

pages = {1533},

publisher = {Copernicus GmbH},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Davila2013toolkit,

title = {A toolkit for groundwater mean residence time interpretation with gaseous tracers},

author = {P. D\'{a}vila and C. K\"{u}lls and M. Weiler},

year  = {2013},

date = {2013-01-01},

journal = {Computers \& Geosciences},

volume = {61},

pages = {116\textendash125},

publisher = {Pergamon},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Klaus2013macropore,

title = {Macropore flow of old water revisited: experimental insights from a tile-drained hillslope},

author = {J. Klaus and E. Zehe and M. Elsner and C. K\"{u}lls and J. J. McDonnell},

doi = {https://doi.org/10.5194/hess-17-103-2013},

year  = {2013},

date = {2013-01-01},

journal = {Hydrology and Earth System Sciences},

volume = {17},

number = {1},

pages = {103},

publisher = {Copernicus GmbH},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Garvelmann2012porewater,

title = {A porewater-based stable isotope approach for the investigation of subsurface hydrological processes},

author = {J. Garvelmann and C. K\"{u}lls and M. Weiler},

doi = {https://doi.org/10.5194/hess-16-631-2012},

year  = {2012},

date = {2012-01-01},

journal = {Hydrology \& Earth System Sciences},

volume = {16},

number = {2},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Benito2010management,

title = {Management of alluvial aquifers in two southern African ephemeral rivers: implications for IWRM},

author = {G. Benito and R. Rohde and M. Seely and C. K\"{u}lls and O. Dahan and Y. Enzel and S. Todd and B. Botero and E. Morin and T. Grodek},

doi = {https://doi.org/10.1007/s11269-009-9463-9},

year  = {2010},

date = {2010-01-01},

journal = {Water Resources Management},

volume = {24},

number = {4},

pages = {641\textendash667},

publisher = {Springer Netherlands},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Morin2009flood,

title = {Flood routing and alluvial aquifer recharge along the ephemeral arid Kuiseb River, Namibia},

author = {E. Morin and T. Grodek and O. Dahan and G. Benito and C. K\"{u}lls and Y. Jacoby and G. Van Langenhove and M. Seely and Y. Enzel},

doi = {https://doi.org/10.1016/j.jhydrol.2009.02.015},

year  = {2009},

date = {2009-01-01},

journal = {Journal of Hydrology},

volume = {368},

number = {1-4},

pages = {262\textendash275},

publisher = {Elsevier},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dahan2008dynamics,

title = {Dynamics of flood water infiltration and ground water recharge in hyperarid desert},

author = {O. Dahan and B. Tatarsky and Y. Enzel and C. K\"{u}lls and M. Seely and G. Benito},

doi = {https://doi.org/10.1111/j.1745-6584.2007.00414.x},

year  = {2008},

date = {2008-01-01},

journal = {Groundwater},

volume = {46},

number = {3},

pages = {450\textendash461},

publisher = {Blackwell Publishing Inc Malden, USA},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Klaus2008evaluating,

title = {Evaluating the recharge mechanism of the Lower Kuiseb Dune area using mixing cell modeling and residence time data},

author = {J. Klaus and C. K\"{u}lls and O. Dahan},

doi = {https://doi.org/10.1016/j.jhydrol.2008.06.012},

year  = {2008},

date = {2008-01-01},

journal = {Journal of Hydrology},

volume = {358},

number = {3-4},

pages = {304\textendash316},

publisher = {Elsevier},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Zagana2007chloride,

title = {Chloride, hydrochemical and isotope methods of groundwater recharge estimation in eastern Mediterranean areas: a case study in Jordan},

author = {E. Zagana and M. Obeidat and C. K\"{u}lls and P. Udluft},

doi = {https://doi.org/10.1002/hyp.6390},

year  = {2007},

date = {2007-01-01},

journal = {Hydrological Processes: An International Journal},

volume = {21},

number = {16},

pages = {2112\textendash2123},

publisher = {John Wiley \& Sons, Ltd. Chichester, UK},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Klock2001,

title = {Quantification of Groundwater Recharge-Estimating recharge values using hydrochemical and geological data: A case study from the semiarid Kalahari catchment of northern Namibia},

author = {H. Klock and C. K\"{u}lls and P. Udluft},

year  = {2001},

date = {2001-01-01},

journal = {IAHS Publications-Series of Proceedings and Reports-Intern Assoc Hydrological Sciences},

volume = {269},

pages = {25\textendash32},

publisher = {Wallingford [Oxfordshire]: IAHS, 1981-},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Klock2000estimation,

title = {Estimation of relative recharge values for the northern Kalahari catchment, Namibia},

author = {H. Klock and C. K\"{u}lls and P. Udluft},

year  = {2000},

date = {2000-01-01},

journal = {Journal of African Earth Sciences},

volume = {30},

number = {4},

pages = {47\textendash48},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kuells1995channel,

title = {Channel infiltration study using dye tracers},

author = {C. K\"{u}lls and C. Leibundgut and U. Schwarz and A. P. Schick},

year  = {1995},

date = {1995-01-01},

journal = {IAHS Publications-Series of Proceedings and Reports-Intern Assoc Hydrological Sciences},

volume = {232},

pages = {429\textendash436},

publisher = {Wallingford [Oxfordshire]: IAHS, 1981-},

keywords = {},

pubstate = {published},

tppubtype = {article}

}