Seasonal surface drainage of sloping farmland : a review of its hydrogeomorphic impacts

The combination of runoff-generating areas (saturated soils) and overland flow concentration in features such as drainage ditches makes sloping farmland vulnerable to soil erosion. The establishment of drainage ditches aims at draining the excess of water from the farmland, particularly in areas where soils are saturated in the rainy season. The hydrogeomorphic impacts on the farmland itself and on downstream areas need however also to be studied. Off site, downstream problems comprise higher peak discharges, leading to gully initiation, an increase in sediment load, and flooding problems. On-site problems such as the development of the drainage ditches into (ephemeral) gullies are less documented, although they may be important, as illustrated in the Lake Tana Basin (Ethiopia). The similarities and interactions between ephemeral gully channels and drainage ditches have to be considered to better understand all effects of drainage. Drainage ditches are a potential source of conflict between farmers with different interests and power, as well as between upstream and downstream users. A case study on drainage ditches on sloping farmlands in the Lake Tana Basin showed that nine out of ten catchments had drainage densities by ditches ranging from 53 to 510 m ha−1. Drainage ditches were constructed with an average top width of 27 (±9) cm. A significant correlation was found between stone bund density (physical conservation structures) and ditch drainage density (R = −0·72), in line with the Ethiopian government's ban on drainage ditches in farmlands where stone bunds have been constructed

Advances and Insights into Neurological Practice 2016-17

Papers published by the European Journal of Neurology reflect the broad interest of practicing neurologists in advances in the aetiology, diagnosis and management of neurological disorders. As a general journal, the proportion of papers in the different subject areas reasonably reflects the case load of a practising neurologist. Stroke represents the largest proportion of papers published, including those on pathophysiology (1-23), acute stroke management (24-47) and the outcome of patients who have suffered stroke (48-72). This article is protected by copyright. All rights reserved

Application of mechanistic models for flow distribution and heat transfer in finned tube bundles

The focus of this thesis was heat transfer and pressure drop in staggered tube bundles with solid and serrated fins. The first part of the work dealed with five prediction models, namely PFR's model (1976), Nir's model (1991), Ralston et al.'s HTFS1 model (1997), Chu and Ralston's HTFS2 model (1998) and McIlwain's HTFS3 model (2003). The models all had correlations for prediction of heat transfer and pressure drop, but only PFR and Nir had specific correlations for serrated fins. The correlations were tested for a multitude of tube bundle geometries - both solid finned and serrated finned - and Reynold's numbers, taken from a database containing hundreds of experiments by several investigators. The predicted results were compared to the measured values for heat transfer and pressure drop from the database. The comparison revealed that none of the models could accurately predict both heat transfer and pressure drop, for both solid fin and serrated fin tube bundles. Overall, the most accurate model was PFR, while the least accurate model was HTFS1. An attempt to improve the prediction accuracy of the models' correlations, by introducing corrections based on different geometric parameters, was carried out. This improvement succeeded for some correlations, but failed for others.The correlations that were ultimately found to have the best prediction accuracy were:\begin{itemize}\item For heat transfer, solid fins: Modified Nir, with 76.2 \% of data predicted within $\pm$20 \% and 47.4 \% of data predicted within $\pm$10 \% AND modified HTFS2, with 79.8 \% of data predicted within $\pm$20 \% and 42.4 \% of data predicted within $\pm$10 \%.\item For heat transfer, serrated fins: Modified HTFS3, with 74.1 \% of data predicted within $\pm$20 \% and 51.4 \% of data predicted within $\pm$10 \%.\item For pressure drop, solid fins: Modified PFR, with 92.3 \% of data predicted within $\pm$30 \% and 67.0 \% of data predicted within $\pm$15 \% AND modified Nir, with 89.6 \% of data predicted within $\pm$30 \% and 71.2 \% of data predicted within $\pm$15 \%.\item For pressure drop, serrated fins: Original PFR, with 64.6 \% of data predicted within $\pm$30 \% and 40.2 \% of data predicted within $\pm$15 \%.\end{itemize}The second part of the work was participation in pressure drop and heat transfer testing of one tube bundle geometry. The bundle consisted of 8 longitudinal tubes and 4 transversal tubes in a staggered layout, with a layout angle of 30$^\circ$. The tubes had an outer diameter of 31.75 mm. The fins were of the I-foot serrated type, with a total fin height of 18 mm, fin thickness 1 mm and fin pitch 3.62 mm. The pressure drop tests were done in the flow range 3.4\e{3}\leq Re \leq 4.1\e{4}. The heat transfer tests were done in the flow range 6.4\e{3}\leq Re \leq 3.4\e{4} with inlet air temperature around 120-130$^\circ$C. The results of the testing showed pressure drop and heat transfer values in a plausible range, but with very high pressure drop uncertainty for low Re. The experimental values were compared to values calculated with the five prediction models. The measured pressure drop and heat transfer were found to best agree with the predictions of Nir and PFR, respectively

Expanding Oil and Gas Activities on the North Slope of Alaska

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Koncentracja biogenów w rolniczych zlewniach na przykładzie zlewni rzeki Skuterud i Zagożdżonki

In this paper, two rural catchment- the Zagożdżonka catchment in Poland and the Skuterud catchment in Aas, Akershus county in Norway are compared. In addition to the general description, more in particular information, runoff, NO3 load, P-PO4 load, total phosphorus and total nitrogen concentrations in streams are compared. The data compared are from 1993 to 1995 in Zagożdżonka catchment and from 1994- 1996 from Skuterud catchment. The average concentration of N-NO3 in Zagożdżonka River in the period was 0.85 mg•1-1 and the mean concentration of P-PO4 was 0.13 mg•l-1. In the stream in Skuterud catchment the average concentration of N-NO3 was 4.95 mg•1-1 and the mean concentration of P-PO4 was 0.04 mg•l-1. For both catchments the same data were also compared for the 2008. In Skuterud catchment the highest concentration of nutrients occurred in November, March and April, which was connected to the higher runoff from agricultural areas during the snowmelt period. In Zagożdżonka catchment the highest concentration of nutrients was noted in March, April and in summer time, which was connected to periods with high amounts of precipitation. Comparison of the two rural catchments showed many differences in applied measurement methods for water sampling, water measurement, discharge measurement, runoff amounts and management practices, which had an effect on results of monitoring program. The compared data can be useful to predict the development of future environmental conditions for example water quality. It can also be useful for predict how nutrient runoff will be in future. What is more the different conditions for runoff in Skuterud and Zagożdżonka then different measures are needed.W artykule zostały porównane dwie rolnicze zlewnie, jedna zlokalizowana w Polsce- Zagożdżonka, druga w Norwegii- Skuterud. Poza ogólnymi opisami zlewni, porównywane informacje dotyczyły szczegółowych danych o opadach, spływie powierzchniowym, oraz stężeniach N-NO3, P-PO4, TP i TN w płynących wodach powierzchniowych. Dane ze zlewni Zagożdżonka pochodzą z lat 1993-1995, ze zlewni Skuterud z lat 1994-1996. Średnie stężenie N-NO3 w w badanym okresie w rzece Zagożdżonka wynosiło 0,85 mg•l, zaś średnie stężenie P-PO4 było równe 0,13 mg•l. W ciekach zlewni Skuterud średnia koncentracja N-NO3 wynosiła 4,95 mg•l, zas P-PO4 oscylowała około 0,04 mg•l. W obydwu przypadkach te same analizy były przeprowadzone i porównane dla roku 2008. Wyniki pokazały, że dla cieków zlokalizowanych w Skuterud najwyższa koncentracja nutrientów wystąpiła w listopadzie, marcu i kwietniu. Zaistniała sytuacja ma związek z wysokim spływem powierzchniowym z terenów rolnych podczas upraw ziemi oraz z okresami roztopów. W zlewni Zagożdżonki najwyższe stężenie nutrientów w rzece odnotowano w marcu, kwietniu oraz w okresie letnim, co miało związek z dużymi opadami w tym okresie. Porównanie dwóch rolniczych zlewni pokazało wiele różnic, miedzy innymi w stosowanych metodach pomiarowych, systemie monitoringowym i otrzymanych wynikach. Mimo wielu różnic przeprowadzona analiza może być przydatna w prognozowaniu przyszłych zmian warunków środowiskowych

Evalution of the WEPP - Profile Model : A Preliminary Study of the Applicability in Norway

AnglBibliogr.: p. 19 (6 pavad.)Vytauto Didžiojo universitetasŽemės ūkio akademij