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Author |
Heaton, T.H.E.; Talma, A.S.; Vogel, J.C. |
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Title |
Origin and history of nitrate in confined groundwater in the western Kalahari |
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Journal Article |
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Year |
1983 |
Publication |
Journal of Hydrology |
Abbreviated Journal |
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62 |
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1 |
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243-262 |
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Data are presented for nitrate, dinitrogen and argon concentrations and 15N14N ratios in groundwater, with radiocarbon ages up to 40,000 yr. for three confined sandstone aquifers in the western Kalahari of South West Africa/Namibia. The nitrate is probably generated within the soil of the recharge areas, and its production rate during the period 3000-40,000 B.P. has remained between 0.5 and 1.6 meq NO−3l−1 of recharge water, with ° 15N between + 4 and + 8‰. Variations in the amount of nitrate and of “excess air” in groundwater recharge are found, and can only reflect changes in the environmental conditions during recharge. They must therefore be caused by the climatic changes that have taken place during the past 25,000 yr. |
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0022-1694 |
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THL @ christoph.kuells @ heaton_origin_1983 |
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95 |
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Author |
Heaton, T.H.E.; Talma, A.S.; Vogel, J.C. |
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Title |
Origin and history of nitrate in confined groundwater in the western Kalahari |
Type |
Journal Article |
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Year |
1983 |
Publication |
Journal of Hydrology |
Abbreviated Journal |
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Volume |
62 |
Issue |
1 |
Pages |
243-262 |
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Abstract |
Data are presented for nitrate, dinitrogen and argon concentrations and 15N14N ratios in groundwater, with radiocarbon ages up to 40,000 yr. for three confined sandstone aquifers in the western Kalahari of South West Africa/Namibia. The nitrate is probably generated within the soil of the recharge areas, and its production rate during the period 3000-40,000 B.P. has remained between 0.5 and 1.6 meq NO−3l−1 of recharge water, with ° 15N between + 4 and + 8‰. Variations in the amount of nitrate and of “excess air” in groundwater recharge are found, and can only reflect changes in the environmental conditions during recharge. They must therefore be caused by the climatic changes that have taken place during the past 25,000 yr. |
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0022-1694 |
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THL @ christoph.kuells @ Heaton1983243 |
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282 |
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Vogel, J.C.; Talma, A.S.; Heaton, T.H.E. |
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Title |
Gaseous nitrogen as evidence for denitrification in groundwater |
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Journal Article |
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Year |
1981 |
Publication |
Journal of Hydrology |
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50 |
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191-200 |
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By investigating the nitrate, oxygen, nitrogen and argon concentrations and 15N14N ratios in artesian groundwater with radiocarbon ages ranging up to 27,000 yr. a process of very slow denitrification in a confined aquifer is demonstrated. The calculated nitrogenisotope fractionation factor associated with this reaction is comparable to that reported for bacterial cultures in vitro and in vivo. |
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0022-1694 |
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THL @ christoph.kuells @ Vogel1981191 |
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280 |
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Author |
Lightfoot, D.R. |
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Title |
Moroccan khettara: Traditional irrigation and progressive desiccation |
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Year |
1996 |
Publication |
Geoforum |
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27 |
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2 |
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261-273 |
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A 300 km network of khettara (qanat) subsurface irrigation channels was excavated in the Tafilalt basin beginning in the late 14th century. More than 75 of these chains provided perennial water following the breakup of the ancient city of Sijilmassa. Khettara continued to function for much of the northern oasis until the early 1970s, when new technologies and government policies forced changes. Data on origins, maintenance, and current use were collected from archival sources, aerial photographs, Landsat imagery, and from interviews. Insufficient water resources and unsustainable practices have dramatically lowered the water table, drying up khettara. This has resulted in a loss of local control over water resources, abandonment of a sustainable irrigation system, and progressive desiccation. |
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0016-7185 |
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THL @ christoph.kuells @ Lightfoot1996261 |
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257 |
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Author |
Eliades, M.; Bruggeman, A.; Djuma, H.; Christofi, C.; Kuells, C. |
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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 |
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Journal Article |
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Year |
2022 |
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Water |
Abbreviated Journal |
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14 |
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5 |
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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. |
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2073-4441 |
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THL @ christoph.kuells @ Marinos2022 |
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82 |
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Author |
Eliades, M.; Bruggeman, A.; Djuma, H.; Christofi, C.; Kuells, C. |
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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 |
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Journal Article |
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2022 |
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Water |
Abbreviated Journal |
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14 |
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5 |
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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. |
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2073-4441 |
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Call Number |
THL @ christoph.kuells @ w14050734 |
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81 |
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Author |
Eliades, M.; Bruggeman, A.; Djuma, H.; Christofi, C.; Kuells, C. |
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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 |
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Journal Article |
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2022 |
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Water |
Abbreviated Journal |
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14 |
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5 |
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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. |
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2073-4441 |
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THL @ christoph.kuells @ w14050734 |
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85 |
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Author |
Aldawsari, S.; Kampmann, R.; Harnisch, J.; Rohde, C. |
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Title |
Setting Time, Microstructure, and Durability Properties of Low Calcium Fly Ash/Slag Geopolymer: A Review |
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2022 |
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Materials |
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15 |
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3 |
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Ordinary Portland cement (OPC) is known for its significant contribution to carbon dioxide emissions. Geopolymer has a lower footprint in terms of CO2 emissions and has been considered as an alternative for OPC. A well-developed understanding of the use of fly-ash-based and slag-based geopolymers as separate systems has been reached in the literature, specifically regarding their mechanical properties. However, the microstructural and durability of the combined system after slag addition introduces more interactive gels and complex microstructural formations. The microstructural changes of complex blended systems contribute to significant advances in the durability of fly ash/slag geopolymers. In the present review, the setting time, microstructural properties (gel phase development, permeability properties, shrinkage behavior), and durability (chloride resistance, sulfate attack, and carbonatation), as discussed literature, are studied and summarized to simplify and draw conclusions. |
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1996-1944 |
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THL @ christoph.kuells @ ma15030876 |
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84 |
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Author |
de Jong, I.J.H.; Arif, S.S.; Gollapalli, P.K.R.; Neelam, P.; Nofal, E.R.; Reddy, K.Y.; Röttcher, K.; Zohrabi, N. |
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Title |
Improving agricultural water productivity with a focus on rural transformation* |
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Journal Article |
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2021 |
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Irrigation and Drainage |
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70 |
Issue |
3 |
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458-469 |
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irrigation efficiency, water productivity, rural transformation, efficacité de l’irrigation, productivité de l’eau, transformation rurale |
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ABSTRACT As a result of population growth, economic development and climate change, feeding the world and providing water security will require important changes in the technologies, institutions, policies and incentives that drive present-day water management, as captured in Goal 6.4 of the Millennium Development Goals. Irrigation is the largest and most inefficient water user, and there is an expectation that even small improvements in agricultural water productivity will improve water security. This paper argues that improvements in irrigation water productivity involves a complex and comprehensive rural transformation that goes beyond mere promotion of water saving technologies. Many of the measures to improve water productivity require significant changes in the production systems of farmers and in the support provided to them. Looking forward, water use and competition over water are expected to further increase. By 2025, about 1.8 billion people will be living in regions or countries with absolute water scarcity. Demand for water will rise exponentially, while supply becomes more erratic and uncertain, prompting the need for significant shifts of inter-sectoral water allocation to support continued economic growth. Advances in the use of remote sensing technologies will make it increasingly possible to cost-effectively and accurately estimate crop evapotranspiration from farmers’ fields. |
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THL @ christoph.kuells @ https://doi.org/10.1002/ird.2451 |
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89 |
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Severi, A.; Masoudian, M.; Kordi, E.; Roettcher, K. |
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Title |
Discharge coefficient of combined-free over-under flow on a cylindrical weir-gate |
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2015 |
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ISH Journal of Hydraulic Engineering |
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21 |
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1 |
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42-52 |
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Taylor & Francis |
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THL @ christoph.kuells @ doi:10.1080/09715010.2014.939503 |
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88 |
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