Changes in mineral composition and depositional environments recorded in the present and past basin-fill sediments of the Kathmandu Valley, central Nepal

Quatenary fluvio-lacustrine basin-fill sediments in the southern part of the Kathmandu Basin was studied in order to clearify the stratigraphy and reconstruct the sedimentary environment during the initial stage of the Paleo-Kathmandu Lake. Six stratigraphic units; Tarebhir, Lukundol, Itaiti, Kalimati, Sunakothi Formations and Terrace gravel deposits, have been described based on field observation of lithology and sediment distribution. The Tarebhir Formation is the basal unit which is overlained by alluvial fan of the Itaiti Formation in the southern part and by the marginal lacustrine deposit of the Lukundol Formation towards the northern part. Further 3 km toward the north from the basin margin at Jorkhu the the Lukundol Formation is overlain by the open lacustrine facies of the Kalimati Formation. At the same locality the latter is overlain by fluvio-lacustrine facies of the Sunakothi Formation. Moreover, the Terrace gravel deposits erosionally cover the Sunakothi Formation. The Kalimati Formation thickens northward, while the Sunakothi Formation thickens between the central and southern part of the basin. The study shows that the Sunakothi Formation is of fluvio-lacustrine (fluvial, deltaic and shallow lacustrine) origin and extends continuously from the southern margin (~1400m amsl) to the central part (~1300m amsl) of the basin. It also indicates that sediments of this formation were deposited at the time of lake level rise and fall. Thick gravel sequence in the southern margin represents the alluvial fan before the origin (before 1 Ma) of the Paleo-Kathmandu Lake, while thick gravel sequence situated above the Sunakothi Formation is the Terrace gravel deposits of the late Pleistocene age (14C method), deposited during and after the shrinkage of the Paleo-Kathmandu Lake from south to north. doi: 10.3126/bdg.v11i0.1544 Bulletin of the Department of Geology, Tribhuvan University, Kathmandu, Nepal, Vol. 11, 2008, pp. 61-70

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Arsenic and other heavy metals in the rivers of central Nepal

Journal of Nepal Geological Society ◽

10.3126/jngs.v31i0.249 ◽

1970 ◽

Vol 31 ◽

pp. 11-18 ◽

Cited By ~ 1

Author(s):

Steven H Emerman

Keyword(s):

Heavy Metals ◽

Kathmandu Valley ◽

Bed Sediment ◽

Multiple Sources ◽

Central Nepal ◽

Naturally Occurring ◽

River Bed ◽

Organic Complexation ◽

Positively Charged ◽

River Bed Sediment

The objective of this study was to measure fluvial As, Co, Cu, Fe, and Zn in order to determine whether central Nepal has a geographically-limited source of As. Seventeen rivers in central Nepal outside and eight rivers inside the heavily polluted Kathmandu valley were sampled monthly for six months. Outside the Kathmandu valley, fluvial As (11 ± 1 mg/l), Co (110 ± 30 mg/l), Cu (93 ± 4 mg/l), Fe (550 ± 80 mg/l), and Ni (50 ± 3 mg/l) were over 5, 550, 13, and 13 times the global averages for each respective element, while Zn (27 ± 4 mg/l) was very close to the global average. The only statistically significant differences between inside and outside the Kathmandu valley were pH (inside: 7.13 ± 0.06, outside: 8.13 ± 0.06), Fe (inside: 1060 ± 90 mg/l) and Cu (inside: 70 ± 10 mg/l) so that Co, Cu, Ni, and Zn levels inside the Kathmandu valley were all naturally occurring. Fluvial As was correlated both in space and time with pH. Outside the Kathmandu valley, fluvial As decreased when pH decreased, due to the increase in the number of positively-charged sorption sites on river bed sediment. Inside the polluted Kathmandu valley, fluvial As increased when pH decreased, due to the organic complexation of As and the negative correlation between organic matter and pH. Central Nepal has multiple sources of As associated with mineralisation of Co, Cu, Fe, and Ni, but not Pb-Zn.

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Danuwargaun Fault as a trigger for draining of the Palaeo-Kathmandu Lake, central Nepal

Journal of Nepal Geological Society ◽

10.3126/jngs.v25i0.32061 ◽

2001 ◽

Vol 25 ◽

Author(s):

Harutaka Sakai

Keyword(s):

Flow Direction ◽

Normal Fault ◽

Kathmandu Valley ◽

Central Nepal ◽

Southern Margin ◽

Bagmati River

A normal fault named as the Danuwargaun Fault was discovered in the southern margin of the Kathmandu Valley. The fault is trending NE-SW and dipping 80 to 90°at NW. The secondary minor faults run along the fault, and a sand dyke intrudes into flu vial beds, trending N 54°E with dip of 80° toward NW. As the northeastern extension of the fault seems to cut the Lukundol Formation and terrace gravel of the Chapagaun Formation (Shrestha et al. 1998), the fault might be active. A change of flow direction of the Bagmati River from N-S to NE-SW near the fault exposure suggests that the draining of the Palaeo-Kathmandu Lake was possibly caused by faulting in the southern margin of the valley.

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Late Pleistocene plant macrofossils from the Thimi Formation (Madhyapur Thimi section) of the Kathmandu Valley, central Nepal

Journal of Nepal Geological Society ◽

10.3126/jngs.v40i0.23594 ◽

2010 ◽

Vol 40 ◽

pp. 31-48 ◽

Cited By ~ 4

Author(s):

Sudarshan Bhandari ◽

Khum N. Paudayal ◽

Arata Momohara

Keyword(s):

Late Pleistocene ◽

Plant Macrofossils ◽

Kathmandu Valley ◽

Thick Section ◽

Common Elements ◽

Central Nepal ◽

Cool Temperate ◽

The Common ◽

Warm Temperate ◽

Climatic Elements

The Late Pleistocene plant macrofossils from the Thimi Formation of the Kathmandu Valley have been reported in this paper. On the basis of 71 taxa from 39 families, seven plant macrofossil assemblages T-1 to T-7 were described from 18.5 m thick section of the Thimi Formation exposed at Madhyapur Thimi, Bhaktapur. Pinus, Abies, Tsuga, Carpinus, Sambucus, Rubus, Eurya, Potentilla and Scirpus are the common elements in the Thimi Formation. It is found that the cool temperate elements (Abies, Pinus, Tsuga, Picea, Taxus) were dominated over warm climatic elements (Quercus, Eurya, Pyracantha, etc.) during the deposition of the Thimi Formation. The underlying Gokarna Formation exhibited subtropical to warm temperate vegetation with the dominance of subtropical elements such as Eurya, Ficus, Zizyphus, etc. over temperate elements like Betula, Tsuga and Abies. During the depositional period of the Thimi Formation, this subtropical to warm temperate type of vegetation shifted to warm to cold temperate type with the abundant presence of gymnosperms and other evergreen taxa.

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Vegetation and Climate Around 780 Kyrs BP in Northern Kathmandu Valley, Central Nepal

Bulletin of the Department of Geology ◽

10.3126/bdg.v20i0.20722 ◽

2018 ◽

pp. 37-48

Author(s):

Sima Humagain ◽

Khum N. Paudayal

Keyword(s):

Cold Climate ◽

Middle Pleistocene ◽

Kathmandu Valley ◽

Tree Pollen ◽

Bottom Part ◽

Central Nepal ◽

Water Plants ◽

Palynological Study ◽

First Time ◽

Vegetation And Climate

Palynological study from the Dharmasthali Formation exposed in the northern part of Kathmandu valley revealed the composition of forest vegetation that were growing in middle Pleistocene (780 kyrs BP) in this area. In a total fifteen samples were collected from the 46 m exposed section for the palynological study. The profile can be divided into two zones on the basis of pollen assemblages. The lower part (DF-I) is dominated by Pteridophyte spores such as Lygodium, Polypodium, Cyathea and Pteris. The dominance of Pteridophytes indicate that the forest floor was moist and humid. The tree pollen consists of Abies, Pinus, Quercus, Podocarpus and Alnus. Other Gymnosperms such as Picea and Tsuga were represented by very low percentage. Poaceae and Cyperaceae show their strong presence indicating grassland and wetland conditions around the depositional basin. In the upper zone (DF-II) there is increase of Gymnosperms such as Picea and Abies. The subtropical Gymnosperm Podocarpus decreased while Tsuga completely became absent in this zone. Cold climate preferring trees such as Cedrus, Betula, Juglans and Ulmus appeared first time in this zone. The climate became even colder and drier in the upper part of the section. Near water plants such as Cyperaceae and Typha show their dominance in this zone. The plant assemblages from bottom part of the Dharmasthali Formation indicate warm climate condition which was becoming colder after 780 kyrs towards the top part of the sequence. Bulletin of Department of Geology, vol. 20-21, 2018, pp:37-48

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Water Quality Index of southern part of the Kathmandu Valley, Central Nepal; evaluation of physical water quality parameters of shallow wells

Bulletin of the Department of Geology ◽

10.3126/bdg.v19i0.19989 ◽

2016 ◽

Vol 19 ◽

pp. 45-56

Author(s):

Bimal Bohara

Keyword(s):

Water Quality ◽

Water Quality Index ◽

Quality Index ◽

Shallow Groundwater ◽

Quality Parameters ◽

Capital City ◽

Kathmandu Valley ◽

Wet Season ◽

Central Nepal ◽

Shallow Wells

Physical water quality of shallow groundwater of the southern part of the Kathmandu Valley was studied and analysed. Being the capital city of the country, the population is increasing day by dayand consequently the demand of water supply has also increased. Analyses reveal ranges of temperature to be 15.3–24.2 °C, pH to be 5.67–8.07, electrical conductivity to be (EC) 230–2860 μS/cm, and dissolved oxygen (DO) to be 0.09–9.1 mg/L in dry season whereas in wet season temperature, pH, EC and DO ranges are respectively 19.6–27.3 °C, 5.92–8.3, 183–3030 μS/cm and 0.19–7.9 mg/L. Water Quality Index (WQI) map shows that the upstream river areas contain good water quality than the downstream areas. The areas like Kalanki and Satdobato have poor water quality according to the guidelines of Nepal Drinking Water Quality Standard.Bulletin of the Department of Geology, Vol. 19, 2016, pp. 45–56

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Status of shallow wells along major rivers of the Kathmandu Valley, Central Nepal

Journal of Nepal Geological Society ◽

10.3126/jngs.v56i1.22697 ◽

2018 ◽

Vol 56 (1) ◽

pp. 31-42 ◽

Cited By ~ 1

Author(s):

Ramita Bajracharya ◽

Naresh Kazi Tamrakar ◽

Manish Shrestha ◽

Bimal Bohara

Keyword(s):

Water Level ◽

Field Measurements ◽

Dry Season ◽

Physical Parameters ◽

Kathmandu Valley ◽

Wet Season ◽

Deep Aquifers ◽

Central Nepal ◽

Shallow Wells ◽

River Corridors

Groundwater is one of the important natural resources to which people of the Kathmandu Valley rely on for their daily purpose. The rate of extraction of groundwater from shallow as well as deep aquifers has increased in the river corridor with the increased urbanization towards the major river corridors in the valley. Wells located within 100 m from the rivers of the Kathmandu Valley were focused in the present study. Altogether 237 wells were recorded from the Bagmati, Manahara and the Bishnumati River corridors of the northern Kathmandu basin, and the Dhobi, Hanumante, Godavari, Kodku, Nakhu and the Balkhu Khola corridors of the southern Kathmandu basin. This research was based on field measurements of well dimension (well diameter, well depth and water level depth) and physical parameters (electrical conductivity, dissolve oxygen, pH and temperature) in April and August of year 2017. The lowest water level was measured in the Nakhu Khola and the highest was measured in the Dhobi Khola in dry season. Average EC ranged between 614.2 μS/cm and 1123.9 μS/cm in dry season, and between 613.0 μS/cm and 916.1 μS/cm in wet season. DO also varied from 1.46 mg/L to 2.46 mg/L in dry season and increased to 1.67–2.53 mg/L in wet season. The lower DO and higher EC in the Balkhu Khola corridor indicates the most contaminated wells in the Kathmandu Valley. Average values of pH and temperature increased in wet season compared to dry season. Average high values of EC and low values of DO were recorded within 30 m distance from the rivers, and EC increased and DO decreased as the distance from river channel increased.

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Bank stability and toe erosion model of the Kodku Khola bank, southeast Kathmandu valley, central Nepal

Journal of Nepal Geological Society ◽

10.3126/jngs.v50i1.22870 ◽

2016 ◽

Vol 50 (1) ◽

pp. 105-111

Author(s):

Ishwor Thapa ◽

Naresh Kazi Tamrakar

Keyword(s):

Riparian Vegetation ◽

Factor Of Safety ◽

Limit Equilibrium ◽

Limit Equilibrium Method ◽

Kathmandu Valley ◽

Bank Stability ◽

Erosion Model ◽

Central Nepal ◽

Settlement Areas ◽

Prehistoric Time

The Kodku Khola is a potential river from the southeast part of Kathmandu valley as it has been used for irrigation and household purposes from prehistoric time. The river is suffering from streambank instability causing great threat to the infrastructure, land and settlement areas. In this context, assessment of Bank Stability and Toe Erosion Model (BSTEM) of the Kodku Khola was undertaken for eight different sites using the BSTEM version 5.4 that calculates a Factor of Safety (Fs) for multilayer streambank, based on limit equilibrium-method. Streambank of the uppermost reach around the transects BK1 (Lower Badikhel) and BK2 (Upper Taukhel) area is stable, where Fs exceeds 1.3 and maximum lateral retreat of channel is 21.86-30.59 cm with 0.025-0.290 m2 of the total eroded area of the bank-toe resulting in less bank toe erosion. Canopy and understorey cover with consolidated bank materials are the causes of stable banks. Streambank of transects BK3 (Arubot) and BK4 (Thaiba) are unstable as Fs ranges from 0.75 to 0.92, and the maximum lateral retreat of channel ranges 70.83-208.81 cm with total eroded bank toe area of 0.117–1.695 m2 resulting in excessive bank toe erosion problems. Major causes of instability are the presence of unconsolidated bank material, high scouring, and sparse riparian vegetation. Within the transects BK6 and BK7 around Harisiddhi, streambanks are stable with less bank toe erosion hazard because of channelization. Where the Fs are low and banks are disturbed by encroachment, suitable bioengineering measures can be implemented to mitigate excessive bank toe erosion and failure.

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Integrated Assessment of Climate Change and Land Use Change Impacts on Hydrology in the Kathmandu Valley Watershed, Central Nepal

Water ◽

10.3390/w11102059 ◽

2019 ◽

Vol 11 (10) ◽

pp. 2059 ◽

Cited By ~ 5

Author(s):

Lamichhane ◽

Shakya

Keyword(s):

Climate Change ◽

Land Use ◽

Assessment Tool ◽

Hydrological Cycle ◽

Satellite Image ◽

Base Flow ◽

Kathmandu Valley ◽

Lulc Change ◽

Central Nepal ◽

Decadal Scale

The population growth and urbanization are rapidly increasing in both central and peripheral areas of the Kathmandu Valley (KV) watershed. Land use/cover (LULC) change and climate variability/change are exacerbating the hydrological cycle in the KV. This study aims to evaluate the extent of changes in hydrology due to changes in climate, LULC and integrated change considering both factors, with KV watershed in central Nepal as a case study. Historical LULC data were extracted from satellite image and future LULC are projected in decadal scale (2020 to 2050) using CLUE-S (the Conversion of Land Use and its Effects at Small regional contest) model. Future climate is projected based on three regional climate models (RCMs) and two representative concentration pathways (RCPs) scenarios, namely, RCP4.5 and RCP8.5. A hydrological model in soil and water assessment tool (SWAT) was developed to simulate hydrology and analyze impacts in hydrology under various scenarios. The modeling results show that the river runoff for RCP4.5 scenarios is projected to increase by 37%, 21%, and 12%, respectively, for climate change only, LULC only, and integrated changes of both. LULC change resulted in an increase in average annual flow, however, a decrease in base-flow. Furthermore, the impacts of integrated changes in both LULC and climate is not a simple superposition of individual changes.

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Palaeoenvironmental analysis of a Miocene basin in the high Taurus Mountains (southern Turkey) and its palaeogeographical and structural significance

Geological Magazine ◽

10.1017/s0016756802006544 ◽

2002 ◽

Vol 139 (4) ◽

pp. 473-487 ◽

Cited By ~ 7

Author(s):

F. OCAKOĞLU

Keyword(s):

Depositional Environments ◽

Coarse Grained ◽

Fault System ◽

Small Scale ◽

The South ◽

Taurus Mountains ◽

The North ◽

South Central ◽

Southern Turkey ◽

Basin Fill

Determination of the relationships between the southern, marine-dominated Miocene basins of south central Turkey and their continental hinterland in southern Turkey has traditionally been frustrated by the apparent absence of basin remnants within the Taurus Mountains. The Dikme basin, which seems to be an enclave of basin remnants within the Aladağ Mountains (Eastern Taurides), consists mainly of coarse-grained continental sediments of various facies. These mostly early–middle Miocene sediments were studied to determine the depositional environments and the factors controlling the basin formation and basin fill architecture, to attempt to close the information gap between the Adana Basin to the south and central Anatolian Miocene further to the north. A generally southwest-flowing axial fluvial system and interfingering coarse-grained marginal alluvial clastics derived from northwest and southeast were identified. The marginal facies to the northwest is bounded by a N 55° E-running structural lineament, that starts from the Ecemiş Fault Zone and in digital elevation models extends toward the north of the study area. Along this lineament, Miocene sediments onlap steep fault-line escarpments. Certain Miocene levels are tectonically disrupted, and an intraformational unconformity and boulder conglomerates are also well-developed in the Miocene sequence. The southeast boundary is similarly defined by a NE-trending fault that periodically elevated the adjacent Tufanbeyli autochthon, producing coarse clastics from this area. This boundary fault also induced fining-upwards vertical patterns and synsedimentary deformation in the marginal facies. Additionally, the central part of the basin exhibits a distinct fault-defined morphology characterized by small-scale (tens of metres to 150 m high) valley-and-sill topography. A thin marine interval was also encountered in the southernmost part of the basin, indicating that the clastic system originating around this area debouched into a Miocene sea situated further to the south. The proposed palaeogeography and basin fill model suggests that the Dikme basin and similar Miocene remnants, all controlled mainly by a northeast-running extensional or transtensional fault system, may have been parts of the terrestrial hinterland that supplied sediment to rapidly subsiding marine areas further south, such as the Adana Basin.

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