The Quantity of Rainfall
The ancient Vedic system provides detailed methods for measuring and predicting the quantity of rainfall. This science combines observation of atmospheric phenomena, astronomical positions, and natural indicators to determine not only when rain will fall, but also how much rain will fall and over what area.
The quantity of rainfall is determined by multiple factors including the number of concomitant phenomena (wind, water, lightning, thunder, clouds), the asterism in which the cloud embryo forms, the month of formation, and various atmospheric conditions during the pregnancy and delivery of clouds.
Units of Measurement
Ancient Vedic system used specific units for measuring rainfall quantity:
| Unit | Value | Description |
|---|---|---|
| Drona | 200 Palas | Primary unit of rainfall measurement |
| Adhaka | 1/4 of a Drona (50 Palas) | Approximately 11 oz. Avoir. |
| Pala | Base unit | Smallest unit of measurement |
Vessel Specification (according to Parasara): A vessel with a circular mouth 20 inches in diameter and depth of 8 inches equals 1 Adhaka capacity.
Rainfall Quantity by Concomitants
The quantity of rainfall depends on which atmospheric phenomena (concomitants) are present:
| Concomitants Present | Quantity | Description |
|---|---|---|
| All five (wind, water, lightning, thunder, cloud) | 1 Drona (200 Palas) | Maximum rainfall with all phenomena present |
| Wind alone | 3 Adhakas (150 Palas) | Rainfall from wind phenomenon |
| Lightning alone | 6 Adhakas (300 Palas) | Rainfall from lightning phenomenon |
| Clouds alone | 9 Adhakas (450 Palas) | Rainfall from cloud phenomenon |
| Thunder alone | 12 Adhakas (600 Palas) | Rainfall from thunder phenomenon |
Area Coverage
The geographical area over which rain will fall depends on the number of phenomena present:
| Number of Phenomena | Area Coverage | Description |
|---|---|---|
| 5 | 100 Yojanas | All five concomitants present |
| 4 | 50 Yojanas | Four concomitants present |
| 3 | 25 Yojanas | Three concomitants present |
| 2 | 12.5 Yojanas | Two concomitants present |
| 1 | 5 Yojanas | One concomitant present |
Pattern: For every phenomenon less, the area coverage is half the extent of the previous one. With only one phenomenon, rain covers 5 Yojanas around.
Duration of Rainfall by Month
Foetuses formed in conjunction with fertile asterisms during these months will yield rain after 195 days for the specified duration:
8
days
Margasirsha
Formation in fertile asterisms
6
days
Pushya
Formation in fertile asterisms
16
days
Magha
Formation in fertile asterisms
24
days
Phalguna
Formation in fertile asterisms
20
days
Chaitra
Formation in fertile asterisms
3
days
Vaisakha
Formation in fertile asterisms
Effects of Excessive Rainfall
Negative Effects of Too Much Rain
Excessive rainfall at the time of cloud formation can have detrimental effects:
| Condition | Effect | Severity |
|---|---|---|
| Rainfall exceeds 1/4 Drona at formation | Miscarriage of cloud embryo | Critical |
| Too much rain without apparent reason | Destruction of foetuses | High |
| Water retained beyond proper time | Rain becomes hard (like milk retained too long) | Moderate |
Effects of Deficient Rainfall
Effects of Insufficient Rain
Lack of proper conditions during cloud formation results in reduced rainfall:
| Condition | Effect | Severity |
|---|---|---|
| Embryo loses too much water at formation | Produces only a drizzle at delivery | Low yield |
| Lack of concomitant signs | Reduced rainfall quantity and area | Moderate yield |
Key Principles of Rainfall Quantity
- Five Concomitants: Wind, water, lightning, thunder, and cloud determine both quantity and area of rainfall.
- Maximum Rainfall: 1 Drona (200 Palas) when all five concomitants are present.
- Individual Contributions: Thunder contributes most (12 Adhakas), followed by clouds (9), lightning (6), and wind (3).
- Area Coverage: Ranges from 100 Yojanas (all five phenomena) to 5 Yojanas (one phenomenon), halving with each missing phenomenon.
- Duration Varies by Month: From 3 days (Vaisakha) to 24 days (Phalguna) depending on formation month.
- Measurement Units: 1 Drona = 4 Adhakas = 200 Palas; 1 Adhaka ≈ 11 oz. Avoir.
- Vessel Specification: Circular mouth 20 inches diameter, 8 inches depth = 1 Adhaka capacity.
- Excessive Rain Warning: More than 1/4 Drona at formation causes miscarriage of cloud embryo.
- Deficient Water: Embryo losing too much water at formation produces only drizzle at delivery.
- Timing Matters: Water retained beyond proper time becomes hard, like milk retained too long.
- Fertile Asterisms: Purvabhadra, Uttarabhadra, Purvashadha, Uttarashadha, and Rohini yield plenty of rain.
- Gestation Period: 195 solar days from formation to rainfall delivery.
Practical Application
This ancient system provides a comprehensive framework for predicting not just when rain will fall, but also how much rain to expect and over what geographical area. By observing the concomitant phenomena and astronomical positions, astrologers could advise farmers and kingdoms on agricultural planning and water resource management.