Abstract: Estimating Evapotranspiration Demands of Different Land Cover Using Diurnal Signals in Dry Season Stream Discharge (2015 AGU Fall Meeting)

H31D-1445
Estimating Evapotranspiration Demands of Different Land Cover Using Diurnal Signals in Dry Season Stream Discharge

Wednesday, 16 December 2015

Poster Hall (Moscone South)

Ravinder Singh Bhalla¹, Kumaran K¹, V Srinivas¹ and Jagdish Krishnaswamy², (1)Foundation for Ecological Research Advocacy and Learning, Pondicherry, India, (2)Ashoka Trust for Research in Ecology and the Environment (ATREE), Centre for Biodiversity and Conservation, Bangalore, India

Abstract:

We use a paired catchment approach to compare the dry season flows between natural grasslands and introduced plantations of black wattle (Acacia mearnsii) in the Nilgiri South range forest which lies in the southern parts of the Western Ghat mountain range in Sothern India, a global biodiversity hot-spot.

Discharges were measured using a portable flume and a weir fitted with capacitance probes logging water levels every five minutes in two adjacent catchments. Sensor artefacts in the data were filtered out before analysis. Diurnal variations in dry season flows from March 1st to April 15th, 2014 were used to estimate the daily ET based on Boronina et al. 2005 (Hyd. Proc. 19, 20, pp. 4055–4068.) using the equation 1. :

E T^{d a i l y} = \sum_{i = 1}^{24} (Q_{m a x} - Q_{i}) Δ t

E T^{d a i l y}

is the daily loss of water from the catchment through ET,

Q_{m a x}

is the daily maximum flow rate in the river,

Q_{i}

is the average flow rate for every hour of the day and

Δ t

Our results show that land use conversion from grasslands to wattle has increased ET by 40.97mm which is to the order of 60% during the period of the study (table 1). This has immediate relevance for dry season flows in the region. Nilgiris provide 40% of the total hydro-power generation for the state of Tamil Nadu and these streams sustain biodiversity and are tributaries of the Cauvery river, the largest the state. They also highlight the potential consequences of programmes such as the National Mission for Greening India which explicitly targets conversions of 10m ha of degraded forests, scrub and grasslands to tree cover and forest.