The research team, led by Muhammad Abrar Faiz and Liangliang Zhang of Northeast Agricultural University in Harbin, China, together with colleagues across China, the United Arab Emirates, Pakistan and Vietnam, confronted a long-standing uncertainty in hydrology. Scientists have known for decades that rivers are fed by two distinct pathways: quickflow, the rapid runoff generated when rain falls faster than the ground can absorb it, and baseflow, the delayed discharge of water that infiltrated the landscape weeks, months or even years earlier. What remained unclear was how strongly baseflow buffers rivers during droughts, and whether that buffering behaves consistently across different climates, geologies and continents. Without that knowledge, drought forecasts and water management plans risked misjudging how long rivers can keep flowing once the precipitation stops.

To resolve the question, the team assembled three complementary streams of evidence: observations from a global network of streamflow gauges, satellite-derived estimates of terrestrial water storage, and simulations from the CMIP6 generation of climate models used in international assessments. From these they constructed two new metrics. The first, the drought-sustained fraction, or DSF, expresses the share of drought-period streamflow that is contributed by baseflow. The second, the additive baseflow buffering index, or BBI, measures how much the baseflow fraction during drought departs from the climatological baseflow index, the long-term average proportion of river flow that comes from slow storage release. Together, the two indices allow researchers to distinguish between rivers that lean harder on groundwater when drought bites and rivers whose slow-flow contribution collapses along with everything else.

The results paint a coherent global picture. Under severe meteorological drought, 74.2 percent of the stations analyzed showed a positive buffering index, meaning the relative contribution of baseflow to streamflow strengthened as conditions dried. A further 12.7 percent of stations showed little change, while 13.1 percent actually registered a decline in the baseflow fraction, a signal that in some catchments even the stored water reserves become depleted or disconnected from the channel. In other words, at most of the world’s monitored rivers, drought does not simply shrink the stream; it transforms the character of the water in it, shifting the balance decisively toward old, slowly released groundwater rather than fresh surface runoff.

The mechanics behind this shift are rooted in the different response times of the two flow pathways. Quickflow depends on recent rainfall and near-surface saturation, so it collapses quickly once precipitation ceases. Baseflow, by contrast, is governed by the gradual drainage of water stored in soils, shallow aquifers and deeper geological formations, which continues to release water to channels long after the storm clouds have gone. The study found that the buffering index increased with low-flow severity and with the magnitude of the streamflow deficit, while baseflow retention declined. That combination indicates that quickflow generally decreased more rapidly than baseflow during droughts, so even as the absolute volume of baseflow diminished, its share of the shrinking river grew. The river becomes, in effect, a progressively more groundwater-dominated system as the drought deepens.

Perhaps the most consequential finding concerns the future. By comparing present-day flow partitioning with CMIP6 climate projections, the researchers discovered that how a catchment divides its water between quickflow and baseflow today constrains how its slow-flow behavior will unfold under warming. Catchments that currently rely heavily on storage release are likely to maintain that character, and the vulnerabilities embedded in present-day storage dynamics will carry forward into a hotter, more drought-prone world. This persistence means that the baseflow buffering observed now is not a transient curiosity but a structural property of each landscape, one that water managers can measure today and use to anticipate tomorrow’s low-flow regimes.

The implications ripple outward well beyond hydrology. Environmental flows that sustain fish, mussels and riverine vegetation during dry seasons depend almost entirely on baseflow in most of the world’s rivers, so the study provides a physical basis for setting drought-era flow thresholds. Water utilities drawing from rivers during droughts are, often unknowingly, harvesting groundwater discharged to the surface, which links surface-water allocation decisions directly to aquifer management. Agricultural regions that irrigate from shrinking streams are tapping the same slow-release reserves, and the 13 percent of stations where the baseflow fraction declined serve as a warning: where storage is exhausted or the connection between aquifer and channel is broken, even the groundwater safety net can fail.

The work also carries a methodological lesson for the modeling community. Because terrestrial water storage observations from satellite gravimetry were woven together with gauge records and climate model output, the study demonstrates how multi-source data can constrain processes that no single dataset captures alone. Climate models have historically struggled to represent groundwater discharge and storage-release dynamics realistically, and the finding that present-day partitioning predicts future slow-flow behavior offers a benchmark against which model simulations can be evaluated. Regions flagged by the analysis as having weak buffering, where baseflow declines during drought, deserve particular scrutiny in projections, since rivers there may lose flow faster than average models suggest.

As climate change intensifies the hydrological cycle, droughts are expected to become more frequent, longer and more severe in many regions, placing unprecedented demands on the storage reservoirs that sustain baseflow. This global inventory of drought buffering gives scientists and policymakers a baseline against which to track whether that resilience is eroding. It also elevates groundwater from an invisible afterthought to the central actor in drought narratives: the quiet, slow, subterranean release of stored water is what keeps rivers flowing, wetlands wet and ecosystems breathing when the sky withholds its share. Protecting recharge areas, managing aquifer withdrawals and preserving the landscape’s capacity to store water are therefore not peripheral concerns but the front line of drought adaptation for the majority of the world’s rivers.

Subject of Research: Global quantification of baseflow contribution to river flow during hydrological droughts

Article Title: Baseflow dominates river flow during droughts across the global streamflow network

Article References: Faiz, M. A., Zhang, L., Liu, D., Fu, Q., Li, M., Zhang, Y., Ma, N., Qi, X., Li, T., Cui, S., Baig, F., Naz, F., & Viet Ha, T. T. (2026). Baseflow dominates river flow during droughts across the global streamflow network. Communications Earth & Environment. https://doi.org/10.1038/s43247-026-04107-5

Image Credits: AI Generated

DOI: 10.1038/s43247-026-04107-5

Keywords: baseflow, hydrological drought, groundwater, streamflow, CMIP6, terrestrial water storage, river flow, low-flow, catchment storage, climate change, hydrology, drought buffering

The team assembled daily rainfall data spanning 123 years, from 1901 to 2024, and subjected it to a battery of statistical tests designed to separate genuine long-term trends from natural variability. They applied the Mann-Kendall test and its modified variant, which corrects for autocorrelation in the time series, alongside Sen’s slope estimator to quantify the magnitude of change. To probe extremes, they used the Peak Over Threshold method, which counts and sizes rainfall events exceeding a defined limit. Drought behaviour was tracked with the Standardised Precipitation Index and the Aridity Index, while low-flow analysis captured how streamflow during dry periods has evolved. The result is a multi-layered diagnosis of a water system under stress from every direction.

The headline finding is deceptively small: an annual decrease in rainfall of 8.4 millimetres per year. That figure alone would not raise alarms, but the monthly breakdown reveals where the damage concentrates. March rainfall is declining at 0.578 millimetres per year, April at 1.419 millimetres per year, July at 1.593 millimetres per year and August at 1.84 millimetres per year, the last being the heart of the monsoon. December, by contrast, shows a marginal increase of 0.005 millimetres per year, statistically negligible in practical terms. The pattern matters because losses in the pre-monsoon months erode the soil moisture and spring recharge that communities depend on before the monsoon arrives, while losses in July and August shrink the total volume available for storage.

Paradoxically, even as total rainfall declines, the extremes are intensifying. The Peak Over Threshold analysis shows that both the frequency and the intensity of extreme rainfall events have been increasing, with a daily deluge of 580 millimetres now assigned a return period of 100 years. This combination, fewer moderate rains and more violent downpours, is a signature increasingly reported across a warming Indian subcontinent, and it is uniquely hostile to water storage. Intense rainfall on degraded or steep terrain runs off rapidly rather than percolating into aquifers, so the water arrives as flood hazard instead of replenishing springs and wells. The study’s findings align with broader evidence that Indian rainfall extremes have grown more spatially variable and more intense even as seasonal totals stagnate or fall.

The hydrological story beneath the surface is equally troubling. By interlinking river stage records, groundwater levels and the region’s geology with the rainfall record, the researchers pieced together a picture of chronically low storage. The Shillong Plateau’s terrain and geology offer limited capacity to hold the enormous volumes that cascade through it during the monsoon, and the low-flow analysis confirms the consequence: streamflow during dry periods is reducing by 0.80 days per year, meaning the rivers run low ever earlier and stay low ever longer. The Aridity Index for July, August and September is decreasing by 0.003 millimetres per year, and the Standardised Precipitation Index reinforces the same conclusion, pointing to intensifying water scarcity through the winter and summer seasons.

What elevates the study beyond a statistical exercise is its socio-hydrological dimension. The researchers combined the secondary data analysis with a community assessment in Nongkya village, using participatory rural appraisal methods to capture how residents experience the scarcity that the numbers describe. The survey found that 61 percent of households experience water scarcity, a figure that independently corroborates the hydro-climatic indicators. This convergence between measured trends and lived experience is precisely what the socio-hydro-climatic framework is designed to achieve: water security is not a function of rainfall alone but of how climate, geology, infrastructure and human demand interact across the year.

The seasonal swing the region endures is extraordinary. The study characterises Cherrapunji’s annual hydro-climatic variability as ranging from hyper-arid and extremely dry conditions to humid and extremely wet ones, a range that few places on Earth experience within a single year. Managing water under such volatility demands infrastructure that can capture monsoon surpluses and carry them through a dry season that is lengthening year by year. Instead, the region’s storages remain low, its springs and streams falter earlier each dry season, and households increasingly face the classic paradox of the wet desert, a term that has been applied to Cherrapunji for nearly two decades as deforestation and land degradation compounded the climatic pressures.

Against this backdrop, the authors propose a set of adaptation strategies grounded in the specific hydrology of the plateau. Micro rainwater harvesting, small-scale capture systems distributed across households and slopes, would intercept some of the intense runoff before it escapes the landscape. Soil and land management aimed at enhancing percolation would help convert violent monsoon downpours into groundwater recharge, addressing the storage deficit at its source. Perhaps most significantly, the researchers argue for integrating traditional knowledge with technological approaches, recognising that Khasi communities have managed this landscape for centuries and that engineered solutions imposed without local insight have historically underperformed. The recommendation echoes a growing consensus in water security research that community-driven, participatory approaches outperform purely top-down interventions.

The implications extend well beyond a single town. Cherrapunji functions as a natural laboratory for the water security challenges that climate change is amplifying across South Asia, where the monsoon is becoming more erratic, extremes more severe, and dry-season stress more acute. The study’s methodological toolkit, combining modified trend tests, extreme-value analysis, drought indices, low-flow assessment and community perception surveys, offers a replicable template for other regions navigating the same transition from predictable seasonality to volatile hydro-climatic whiplash. As the authors make clear, the question for Cherrapunji is no longer whether the rain will fall, but whether anything can be done to keep it from vanishing the moment it does.

Subject of Research: Socio-hydro-climatic analysis of water security and rainfall trends in Cherrapunji, semi-arid India

Article Title: Socio-hydro-climatic analysis for water security in semi-arid India: a case of Cherrapunji, India

Article References: Paul, N., Pushpalatha, R., Roshni, T., Nair, A., Dutta, D., Singh, P. P., & P., A. (2026). Socio-hydro-climatic analysis for water security in semi-arid India: a case of Cherrapunji, India. Regional Environmental Change, 26(4), Article 211. https://doi.org/10.1007/s10113-026-02701-z

Image Credits: AI Generated

DOI: 10.1007/s10113-026-02701-z

Keywords: Cherrapunji, water security, rainfall trends, Mann-Kendall test, Standardised Precipitation Index, aridity index, low flow, groundwater, extreme rainfall, water scarcity, Meghalaya, climate change