Springs in India’s Western Ghats reveal six years of nutrient shifts tied to land use

Springs draining the Western Ghats of India act as sensitive recorders of how rapidly changing tropical landscapes alter groundwater chemistry, according to a six-year study published in Environmental Geochemistry and Health. Between 2018 and 2023, researchers monitored dissolved nutrients and physicochemical conditions in springs across distinct hydrogeological settings in the mountain range, focusing on dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP) and dissolved silica (DSi), alongside electrical conductivity, total dissolved solids and dissolved oxygen.

The measurements revealed significant spatial variability in all of these parameters, confirmed statistically with one-way ANOVA at p < 0.05. The authors attribute this heterogeneity to differences in recharge pathways and land-use influences among the springs. In southern Kerala, springs near Varkala Cliff—sites SK1 and SK2—showed elevated dissolved inorganic nitrogen, while phosphorus remained low with limited year-to-year variation but clear differences between locations. In southern Karnataka, springs DK5 and DK6 stood out for comparatively higher concentrations of both DIP and DIN, and for greater temporal variability than the other springs monitored.

Ratio analysis added a biogeochemical dimension to the pattern. DIN:DIP ratios exceeded 26:1 at the study sites, a level the researchers interpret as nitrogen enrichment with the potential for phosphorus limitation of downstream ecosystems. They caution, however, that this threshold was originally derived from surface-water systems, so its application to spring water is an interpretive extension rather than a directly validated benchmark. Higher DIN:DSi ratios in the Kerala springs contrasted with signatures of silicate weathering in the Karnataka springs, pointing to differences in subsurface flow paths, soil carbon dioxide dynamics and rock–water interaction between the two regions.

To trace the origins of the nitrogen, the team examined Na-normalized Cl/NO3 relationships and NO3/Cl versus Cl plots. These approaches suggested agricultural and sewage inputs as likely sources of the dissolved inorganic nitrogen. The authors are explicit about the limits of this inference: without isotopic tracers such as nitrate isotopes, the source attributions remain indicative rather than definitive.

Land-use analysis reinforced the anthropogenic signal. Built-up area increased substantially over the study period—by roughly 36 percent in the Karnataka study area and about 4 percent in Kerala—supporting the interpretation that expanding development is driving nitrogen loading into the aquifers that feed the springs. The nutrient patterns themselves, however, were not uniform. Dissolved inorganic nitrogen was spatially heterogeneous, with elevated concentrations concentrated at SK1 and SK2 in Kerala and pronounced temporal variability at DK5 and DK6 in Karnataka, rather than following a single, region-wide increasing trend across all sites.

That spatial patchiness is central to the study’s conclusion. The authors argue that tropical spring nutrient chemistry cannot be explained by land-use change alone, nor by geology alone, but reflects the interaction of three factors: the hydrogeological structure that controls how water moves through the subsurface, the biogeochemical processes that transform nutrients along the way, and the land-use transitions that supply the nutrients in the first place. Springs in different settings responded differently to the same regional pressures, which is why the same six-year window produced pronounced temporal variability at DK5 and DK6 in Karnataka and persistently elevated concentrations at SK1 and SK2 in Kerala.

The study’s framing of springs as sentinels carries practical weight. The six-year record shows that these signals are readable: nitrogen enrichment tracks built-up expansion, phosphorus behaves differently and stays low in some settings, and silica ratios fingerprint the weathering environment that the water has passed through.

Several caveats bound the findings. The source attribution rests on molar ratio relationships that the authors themselves flag as suggestive rather than conclusive without isotopic confirmation. The phosphorus-limitation threshold is borrowed from surface-water ecology. And the nutrient record spans a limited set of springs in two southern states, so the patterns documented—elevated DIN near Varkala, higher and more variable DIP and DIN at DK5 and DK6, contrasting weathering signatures between Kerala and Karnataka—describe these specific hydrogeological settings rather than the Western Ghats as a whole. Within those limits, the study documents how groundwater-dependent nutrient exports in a rapidly transforming tropical landscape are jointly shaped by aquifer architecture and human activity, and it establishes a multi-year baseline against which future change in these spring systems can be measured.

Subject of Research: Nutrient dynamics and anthropogenic influences in springs across hydrogeological settings of the Western Ghats, India

Article Title: Springs as sentinels: hydrogeological mediation and anthropogenic forcing of nutrient dynamics in tropical aquifers

Article References: Majee, U., R., S., S., A., Das, P., K., S., & K., M. (2026). Springs as sentinels: hydrogeological mediation and anthropogenic forcing of nutrient dynamics in tropical aquifers. Environmental Geochemistry and Health, 48(16), Article 653. https://doi.org/10.1007/s10653-026-03541-w

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03541-w

Keywords: springs, groundwater, Western Ghats, dissolved inorganic nitrogen, dissolved inorganic phosphorus, dissolved silica, land use change, nitrogen enrichment, phosphorus limitation, hydrogeology, Kerala, Karnataka