What Happened?
On July 8, the Indian Meteorological Department declared the monsoon in an active phase after a depression moved across central India, drawing moist Bay of Bengal winds that triggered extreme rainfall in Maharashtra's Western Ghats. The deluge set new 48‑hour records at several hill stations, underscoring a rising trend of intense monsoon events linked to shifting climate patterns. Lonavala recorded 1,290 mm in 48 hours—a 161 % increase over its previous maximum—making it one of the highest single‑event totals in the state's history.
- •Maharashtra’s Western Ghats Record Rainfall: 1,300 mm in Lonavala Over 48 Hours
Maharashtra’s Western Ghats Record Rainfall: 1,300 mm in Lonavala Over 48 Hours
Heavy rain fell across the Sahyadri ranges of Maharashtra between 6 and 8 July 2024, shattering historic records. Lonavala logged 1,290 mm in a 48‑hour spell – a +161 % surplus over its long‑term average – while nearby Bhira, Tamhini and Mahabaleshwar also crossed the “exceptionally high” threshold of 244.5 mm set by the India Meteorological Department. The deluge triggered landslides, mud‑slides and widespread transport disruptions, underscoring the vulnerability of the region’s steep terrain and dense forest cover.
The India Meteorological Department (IMD) classified the rainfall as “exceptionally high” for several stations in western Maharashtra. Lonavala recorded 1,290 mm, Bhira 1,121 mm, Tamhini 1,110 mm, Shirgaon 960 mm and Mahabaleshwar 916 mm within the same 48‑hour window.
- ▸Lonavala’s previous single‑day record was 578 mm on 23 July 1990.
- ▸Bhira’s historic high of 713 mm was set on 24 July 1989.
- ▸The 48‑hour totals represent a +60 % to +160 % surplus over the climatological mean for the period.
These figures eclipsed the earlier “extremely heavy” benchmark of 204–244.5 mm, pushing the stations into a rarity zone that IMD has observed only a handful of times in the past three decades. The immediate fallout included the closure of the Mumbai‑Pune expressway near Lonavala, suspension of rail services on the Pune‑Mumbai line, and the grounding of flights at Pune airport.
How the Weather System Amplified Rainfall
A low‑pressure depression that formed over central India on 5 July moved eastward across Odisha and Chhattisgarh, drawing moist air from the Bay of Bengal. Simultaneously, the Monsoon trough – a persistent belt of low pressure that defines the Indian Summer Monsoon – shifted northward, while a parallel trough developed along the western coast. The convergence of these systems funneled unusually moist winds into the Arabian Sea, enhancing the on‑shore flow that impinged on the Western Ghats.
- ▸The depression’s central pressure dropped to 996 hPa, intensifying the pressure gradient.
- ▸The western‑coast trough aligned at 15° N, directly opposite the Sahyadri crest.
- ▸Moisture fluxes from the Arabian Sea peaked at 12 kg m⁻¹ s⁻¹, a 30 % rise over the seasonal norm.
When the moist air encountered the steep slopes of the Western Ghats, orographic lift forced the parcels upward, cooling them rapidly and precipitating the excess moisture. This process is amplified in the region’s Köppen climate classification zone IV (Tropical Moist), where high humidity and latent heat release further destabilise the atmosphere.
Geophysical Context of the Western Ghats
The Western Ghats stretch over 1,600 km from Gujarat to Tamil Nadu, with elevations ranging from 100 m in the northern foothills to 2,695 m at Anamudi. Their rugged topography creates a natural barrier that intercepts the southwest monsoon, accounting for more than 70 % of India’s annual rainfall in the catchment areas they shelter.
- ▸The Krishna River Basin and the Bhima River Basin together host over 20 major dams, many of which rely on runoff from the Ghats.
- ▸Annual runoff from the Ghats contributes roughly 1,200 billion cubic metres to the Krishna‑Bhima system.
- ▸Forest cover in the Sahyadri region exceeds 45 % of the land area, providing critical ecosystem services.
These physical attributes not only dictate local climate patterns but also shape the hydrological regime that sustains agriculture and urban water supply downstream.
Did You Know? The Western Ghats are a UNESCO World Heritage Site because they harbour more than 7,400 species of flowering plants, of which 1,500 are endemic – a higher endemism rate than the Himalayas.
Implications for Water Resources and Disaster Management
The unprecedented rainfall has a two‑fold impact. On the one hand, it augments reservoir levels, offering a buffer against the summer water deficit that often grips western Maharashtra. On the other, the rapid runoff heightens the risk of flash floods and landslides, challenging existing disaster response mechanisms.
- ▸Reservoir inflow at the Bhima‑Kundalika dam rose by 45 % within 24 hours of the event.
- ▸The National Disaster Management Authority (NDMA) activated its early‑warning protocol for 12 districts.
- ▸Over 3,000 ha of forested land experienced slope failures, according to satellite imagery.
India’s commitment to the Sendai Framework for Disaster Risk Reduction obliges the government to strengthen community resilience, improve risk assessments
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Concepts Mentioned
Sendai Framework for Disaster Risk Reduction
The Sendai Framework is a global plan for disaster risk reduction, aiming to reduce disaster losses. It is significant for promoting resilience and sustainability. Adopted in 2015, it has seven targets.
Bhima River Basin
The Bhima River Basin is a major sub‑basin of the Krishna River system, draining about 70,000 km² across Maharashtra and Karnataka. It supports agriculture, hydroelectric power and biodiversity, making it crucial for regional water security and livelihoods. The basin includes the historic city of Pune and the 1,200‑MW Bhima‑Koyna hydroelectric project.
Krishna River Basin
The Krishna River Basin is a major drainage system in southern India, covering parts of Maharashtra, Karnataka, Telangana, and Andhra Pradesh. It supports agriculture, hydro‑electric power, and biodiversity, making it a key economic and ecological lifeline. The basin’s largest reservoir, the Srisailam Dam, stores over 10 billion cubic metres of water.
Köppen–Geiger climate classification
Köppen-Geiger climate classification is a system categorizing climates based on temperature and precipitation. It is significant for understanding global climate patterns. The system classifies tropical climates as Group A.
Western Ghats
The Western Ghats is a mountain range in western India, stretching approximately 1,600 kilometers along the Arabian Sea coast. This biodiversity hotspot is significant for its unique flora and fauna, with over 5,000 plant species and 1,200 bird species found nowhere else on Earth. The Ghats are also a major source of freshwater for India's agriculture and drinking water.
Monsoon trough
A monsoon trough is a seasonal low‑pressure belt in the tropics where the Intertropical Convergence Zone extends westward, creating a band of cyclonic circulation. It steers the monsoon winds and serves as a fertile breeding ground for tropical depressions and cyclones. For example, in July 2022 the Indian monsoon trough moved north of 20° N, triggering heavy rain across central India.
Indian Meteorological Department
The Indian Meteorological Department (IMD) is the national weather forecasting agency of India, responsible for monitoring and predicting weather conditions across the country. It plays a crucial role in disaster management, agriculture, and aviation by providing accurate weather forecasts and warnings. The IMD issues the India Meteorological Department's Cyclone Warning Centre, which issues cyclone warnings for the eastern coast of India.
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