Lecture 8: Managing hydrological ecosystem

Question 1

Local impacts (consequences)  of LUCC
(land use and cover change)

Answer 1

Local impacts (consequences)  of LUCC
(land use and cover change)

Question 2

The impact of deforestation on regional climate

Answer 2

Since land surface characteristics control the surface albedo (reflectivity) to short wave (solar) radiation as well as the aerodynamic roughness of the surface, changes in land cover can bring about large scale changes in regional climate.

Question 3

Hydrology, water resources & and land use change

Answer 3

Forest conversion to pasture generally leads to increases in seasonal and annual total streamflow because forests
have a higher surface area than grassland

are aerodynamically rougher than grassland

have an extensive leaf and root network and thus make more water available for evapo-transpiration than grassland

encourage infiltration and local storage/slow seepage over runoff and stormflow because of higher infiltration capacity and increased soil and surface water storage capacities

Question 4

Paired catchment studies

Answer 4

Cannot measure ET (evapo-transp.) at catchment scale so measure P+Q, assume D and ΔS are small

Compare catchments that are similar in all ways but land cover/use

Estimate differences in ET from closing the water balance

Question 5

Experimental manipulations – flow duration curves

Answer 5

1 year after planting higher flows are more frequent

8 years after planting the same flows are rarer

High flows are exceeded more frequently for pasture than forest

Question 6

Soil erosion and sedimentation

Answer 6

After forest destruction soil is in a “pioneer” condition and will be colonised by aggressive weedy plants which compete with new crops for available nutrients.

Erosion can result. Gullying is a more severe and an immediate problem with heavy rainfall.

The inherent low soil fertility of tropical soils is a severe limitation. Fertiliser application soon becomes necessary.

Question 7

Connecting hydrological models with near-real time deforestation products

Answer 7

Terra-i – dynamic, near real-time 16 day monitoring of land cover change based on neural network analysis of MODIS NDVI data Example : land use change Rondonia 2004 to present (more yellow=more recent).

Question 8

Rondonia: % change in net soil erosion

Answer 8

Significant increases in erosion locally at bare sites but much of eroded soil deposited in nearby rivers so may not get far downstream