The river network is one of the important transporters of nutrients from the
environment and land masses to the oceans and regularly provides storage for
several compounds. The variations in suspended and dissolved discharge of the
river are more substantial than the changes in water discharge. (Suspended
and dissolved) organic carbons (SOC and DOC) are imperative segments in the
carbon cycle and fill in as essential food sources for amphibian sustenance
networks. In the present study, 26 samples of water were collected from
different locations over the 642 km stretch of the Ramganga River and its
adjoining tributaries to observe the spatial variation of DOC, dissolved
inorganic carbon (DIC), SOC and suspended inorganic carbon (SIC) in river
water. The DOC and DIC values of Ramganga River goes between 1.49 to 4.65 and
9.61 to 36.6 mg L
The imbalance in the carbon cycle is an outcome of large scale human
activities that enhance the atmospheric CO
The Ramganga River basin with the sampling locations for the present study.
Ramganga River originates from the Dudhotali Mountains in the Chamoli district of Uttarakhand, and flows through the Kumaun Himalayas and the Ganga Flood Plains (GFP) before joining Ganges River (Khan and Chakrapani, 2016) (Fig. 1).
Land Use and Land Cover area of Ramganga Basin.
It has a catchment area of about 22 685 km
Figure 2 shows the average annual temperature, precipitation and water discharge at three gauging site on the Ramganga River. Geologically, the entire basin has been divided into three zones, namely Lesser Himalayas, Sub Himalayas and GFP (Khan et al., 2016c).
10 L of water samples were collected from 26 different locations from
the three stretches of the Ramganga River and its tributaries viz., upper
(RG1–RG6 and T1–T5), middle (RG7–RG11 and T6–T8) and lower (RG12–RG16 and
T9–T10) (Fig. 1). All the sampling has been done in the month March and
April 2014. The suspended sediment concentration (SSC) was obtained by
filtering the water sample using cellulose nitrate membrane filter paper of
0.45
The estimation of TDC, DOC and DIC in the river water was done by liquid module of Analytik Jena TC Analyser Multi N/C 3100 instrument. TSC, SOC and SIC were estimated in the solid module of the same instrument by using calcium carbonate as a standard.
TDC shows very clear increasing pattern from upstream to downstream in case of Ramganga River and its tributaries which indicate the impact of human influence on the river; whereas TSC did not show any consistency in its concentration from upstream to downstream (Fig. 3).
Spatial variation of TSC and TDC in Ramganga River and its tributaries.
DOC and DIC are the two important forms in which dissolved carbon is present
in the river water. There is huge spatial variation has been shown in the
concentration of DOC and DIC in the Ramganga basin. In Ramganga River and
its tributaries, DOC varied from 1.49–4.65 and 0.097–4.52 mg L
According to Sun et al. (2011), for most rivers, bicarbonate is the dominant form of DIC, primarily from chemical weathering of silicates and carbonates in the drainage basin. Soil erosion is the essentially derived source for DOC and SOC in the river which shows higher turbidity values, however, commitment of aquatic biomass may possibly enhance considerably in low turbid rivers (Ludwig et al., 1996).
Spatial variation in the DOC and DIC concentration of the Ramganga River and its tributaries.
Through temporary mechanism, for instance primary production and
respiration, microbial consumption, organic and inorganic carbon in the
river can transform to each other (Sun et al., 2011). The upper reach of the
Ramganga River and its tributaries flowing in Himalayas shows low
concentrations of DOC and DIC as compared to middle and lower reaches and
the value of turbidity is also low in this stretch (Fig. 5). The DIC
concentrations in this reach are mainly attributed to the dilution of
carbonate and silicate rocks by chemical weathering. Forest covers which
occupied > 75 % of the upper region of the Ramganga basin
might be a possible factor for the DOC concentration. Evans et al. (2007)
and Butman et al. (2015) observed that DOC has been regularly of recent
source acclimatized by plants and old carbon (fossilized) includes just
3–9 % of the total DOC conveyed by the global rivers. The
Spatial variation in turbidity values of the Ramganga River and its tributaries.
The huge elevation in the DOC and DIC concentration (Fig. 4) is shown in the middle and lower reaches of the Ramganga River and its tributaries, which is situated in the GFP. This area has largely influenced by dense population and highly industrial and agricultural activities and covers around 66 % area of the total basin. The higher values of DOC in sampling sites RG6 to RG11 and T5 to T8 in Fig. 4a may be due to the non-point sources of pollution from semi-urban and rural areas, human interaction with river such as direct discharge of waste material, mass bathing during festivals, religious funerals and cremation on the bank of river, cattle bathing etc. Whereas, the higher values of DIC from RG6 to RG11 and T5 to T8 in Fig. 4b is mainly attributed to the presence of silicate and carbonate rocks in the upper catchment area, soil erosion, agricultural activities and runoff, sand mining and river meandering etc.
SOC and SIC are the two forms of suspended carbon or particulate carbon (SC or PC) are present in river systems. High concentrations of suspended organic and inorganic matters are a relentless component of numerous substantial streams (Smith et al., 1987). As similar to the dissolved carbon, huge spatial variation has also been shown in the concentration of SOC, whereas SIC does not show the similar pattern in the Ramganga basin (Fig. 6).
Spatial variation in the SOC and SIC concentration of the Ramganga River and its tributaries.
In Ramganga River and its tributaries, SOC varied from 1.31–22.15 and
0.80–47.23 g kg
Panwar et al. (2017), stated that due to variations in topography and rates of chemical weathering, the organic carbon transported by River Ganges mainly in the form DOC in its upstream and mostly as SOC down the Himalayan foothills. The possible factors behind the SIC concentrations in the upper reaches of the basin, which flows through Kumaon Himalayas is may be due to the dilution of carbonate and silicate rocks by chemical weathering. Forest covers which occupied > 75 % of the upper reaches of the Ramganga basin might be a possible factor for the SOC concentration. SC mostly shows positive correlation with SSC (Panwar et al., 2017). In case of Ramganga River and its tributaries, a positive correlation between SSC with SIC and SOC is shown in Fig. 7.
Correlation between SOC and SIC with SSC.
A regular downstream increase pattern in SSC, 4.4 to 66.36 mg L
The significant conclusions of this investigation are as per the following:
The Ramganga river and its tributaries show abundance amount of TSC (SOC
and SIC) and TDC (DOC and DIC) both in the upstream and downstream. TDC accounts more in river concentration as compared to TSC, especially
in the downstream of the river. Urbanization has driven the expansion of fluvial DOC in the Ramganga
basin, which is likely connected to the expansion in sewage discharge
because of expanded population. Agricultural activities and sand mining have also plays significant role
in triggering the river TSC in Ramganga River.
This study only shows the concentration of TSC and TDC on spatial scales,
but in order to get the role Ramganga Basin's in transporting TSC and TDC to
the River Ganges, this study can be further extended to the temporal scale
in order to obtain total carbon flux and role of meteorological factors on
regulating this phenomenon.
Data are available upon request by the corresponding author.
The authors declare that they have no conflict of interest.
This article is part of the special issue “Innovative water resources management – understanding and balancing interactions between humankind and nature”. It is a result of the 8th International Water Resources Management Conference of ICWRS, Beijing, China, 13–15 June 2018.
Mohd Yawar Ali Khan thanks the Indian Institute of Technology, Roorkee, India. The authors gratefully acknowledge the comments of the reviewers and the editor, which enormously improved the presentation of the final manuscript. Edited by: Wenchao Sun Reviewed by: two anonymous referees