Partitioning of rainfall in Acacia species of Indian Thar Desert

Thar desert of India, being a water-scarce area, partitioning of gross rainfall (GR) into throughfall (TF), stemflow (SF) and interception loss (I) has important role in predicting the hydrological effects and also on water balance of the region. Experiments conducted in the farm area of ICAR-Regional Research Station, Central Arid Zone Research Institute, Jaisalmer. Measurements were carried out on a rainfall event basis during July to September, 2012. Data observed for 22 years old Acacia senegal and A. tortilis trees having three DBH gradient. Through fall collectors at the rate of two per tree were placed randomly beneath the canopies and stem flow was collected from same trees using specially designed rubber tube stem flow collection collars. The cumulative gross rain fall(GR) amount of 8 events was 145.10mm. Gross rainfall was measured in an open area close to the study plot. The amount of cumulative GR transformed into TF, SF and I for A. senegal and A. tortilis were (107.57 mm, 10.81 mm and 26.72 mm) and (89.31 mm, 7.85 mm and 47.94 mm), respectively. On the events cale, average ratios of TF:GR,SF:GR, and I:GR for A. senegal and A. tortilis were (74.14%, 7.45% and 18.41%) and (61.55%, 5.41% and 33.04%), respectively. A fairly strong positive correlation was observed between TF:GR and GR for both A. senegal and A. tortilis (R² value – 0.52; 0.67). Negative correlation was observed between SF: GR and GR (R² value – 0.32); I: GR and GR (R² value – 0.44) for A. tortilis, whereas, no correlation was observed between SF:GR and GR (R²value– 0.25); I:GR and GR (R²value– 0.15)for A. senegal. As the intensity of the rainfall events increased, the interception loss in A. senegal (18.41%) was comparatively less than A. tortilis (33.04%). The study concludes that interception in A. tortilis represents are markable percentage of gross rain fall than in A. senegal and it was strongly affected by the amount of GR. The higher TF:GR ratio of Acacia senegal trees may cause for lesser runoff.