Effects of Teak Plantations on Water Supply at KVTC HJ van Hensbergen for Dave Scott

Trees and Water Use  Trees use water to cool.  Trees use water for transport of nutrients.  Trees use water to grow.  Big trees use more water.  Trees with big leaves use more water.  This does not necessarily mean that teak at Kilombero will reduce streamflow.

Hydrology of Kilombero  Rainfall is approximately 1550mm Ranging from less than 1000 C20yr low to more than 2100 C20yr high Ranging from less than 1000 C20yr low to more than 2100 C20yr high  High temperatures lead to high evaporation.  Some water is lost during storms as overland flow.  Rest is effective rainfall. Interception loss Interception loss  Net Rainfall Available to vegetation Available to vegetation  Tree growth at KVTC reflects water availability. Trees use most or all of the water where they grow. Trees use most or all of the water where they grow. Models developed for South Africa can be used to model this situation. Models developed for South Africa can be used to model this situation.

Teak and Streamflow.  If teak was planted over entire catchments it could have a serious effect on streamflow.  The situation at KVTC is different there is likely to be little effect on streamflow.

Area Planted 15000ha of which 3636 could be planted 24%

Position in Catchment Upper Catchment High Rainfall Lower Catchment Low Rainfall Teak

Spread across many Catchments Effect on any one catchment small.

Effects on Streamflow  Baseflow Little effect because there is only a very small surplus over evaporation at teak sites in any case. Little effect because there is only a very small surplus over evaporation at teak sites in any case.  Stormflow Little effect because most of this is from overland flow. Little effect because most of this is from overland flow. Any teak effect would be positive by slowing release and improving interception. Any teak effect would be positive by slowing release and improving interception.

Recommendations of Report  Monitoring of Rainfall  Monitoring of Streamflow  Road design construction and maintenance to reduce possible impact on water quality