Small But Important: The Role of Small Floodplain Tributaries to River Nutrient Budgets

Abstract

The fertile Indo-Gangetic floodplain contains numerous small, rain-fed rivers. These rivers contribute to the river water chemistry of the Ganges River; however, these small floodplain rivers are never studied nor monitored owing to their smaller size with reference to catchment area (∼1000− 10000 km 2 ) and volume of discharge (∼10−100 m 3 /s). Here we quantify the role of a small flood plain river, the Pandu River, in terms of dissolved inorganic nitrogen (DIN) and phosphate export to Ganges River. We present results from time series sampling campaigns over 2015 and 2016. Our result shows that Pandu River exports 793 ± 128 t/yr of DIN and 177 ± 29 t/yr phosphate to the Ganges River, which accounts for 0.1% and 0.42% of the total DIN and phosphate fluxes, respectively, that Ganges River exports into Bay of Bengal. Furthermore, we show that the small floodplain rivers in the Indo-Gangetic floodplain could collectively contribute ∼15% and ∼61% of the DIN and phosphate fluxes, respectively, that Ganges River delivers into Bay of Bengal. Therefore, runoff from small floodplain rivers is an important flux that could contribute to the dissolved nutrient budget of large river systems, and they must be better monitored to address future challenges in river basin management. KEYWORDS: nutrient fluxes, nitrate and phosphate contamination, N and P transport pathways in Indo-Gangetic floodplain, riverine nutrient budget, small floodplain rivers

Nutrient and microbial water quality of the upper Ganga River, India: identification of pollution sources

“…Similar conclusions about P and N loadings from fertilisers and urban wastes have been reached in the study of the Pandu River by Sen et al (2018).…”

“…These vital water quality parameters, routinely measured in more economically developed countries, such as phosphorus and nitrogen species, dissolved organic carbon, metals, pesticides, chlorophyll and major anion concentrations, are now beginning to be captured by recent Indian academic studies, but the data is usually aggregated to mean and range data, either across the seasons or from all monitoring sites along the river (Yadav and Pandey, 2017b;a;Khan et al, 2016b;Matta et al, 2017;Jin et al, 2015;Mariya et al, 2019;Agarwal et al, 2015), thereby losing spatial and temporal resolution. The presentation of water quality data from specific sampling dates are currently extremely rare in Indian river research, but starting to be presented in recent papers (Sen et al, 2018;Khan et al, 2016a;Pandey and Yadav, 2017). However, the situation in India is improving rapidly, with a wider range of water quality parameters now been measured by the regulatory authorities, including sub-daily data from in-situ water quality probes.…”

Metagenomic insights into the functional microbial diversity of the lower stretch of the River Ganga: mapping antibiotic and metal resistance genes

“…Phosphate enrichment in an aquatic environment can occur due to inputs of sewage, fertilizers and from animal waste, in addition to enrichment of nitrogen (Jarvie et al 2006). Such trends have also been observed in other parts of the River Ganga (Bowes et al 2020) as well as in Pandu (Sen et al 2018) and Mississippi Rivers (Alexander et al 2007). High concentrations of dissolved nitrate have been recorded in the upper stretches of Ganga including in Rishikesh and Haridwar.…”

Application of Soil Water Assessment Tool (SWAT) Model in Analyzing Nitrogen Transport Inside the Narmada River Basin

“…This in turn leads to increased usage of fertilizers which are rich in essential nutrients like nitrogen and phosphorus which are required by crops in order to grow. Excessive use of these fertilizers over decadal time scale has led to nutrient pollution in several regions of India (Krishna et al, 2016;Sen et al, 2018). This paper estimates the potential regions of increasing nitrogen concentration and flux, causing nutrient pollution on the river system and people impacted by the water of Narmada River.…”