UNIVERSITY OF ZIMBABWE
MSc Programme in Integrated Water Resource Management (IWRM)
Catchment Management
19th Sept 2003
The examination comprises of 6 Questions.
IWRM 6.2
Time allowed: 3 hours
Answer 5 questions only.
All questions carry equal marks.
This examination consists of 3 pages
Question 1 SCALE INTERACTIONS IN CATCHMENT MANAGEMENT (20
marks)
Runoff generation at the catchment level will depend on the land use in the catchment
area. The runoff generated in a river basin, is determined from the aggregate (total)
runoff generation from land uses in the catchments and losses of water during its
journey through the landscape from upstream to downstream.
1) Describe, using the concept of hydronomic zones, the major water functions of
different spatial units in a river basin. Focus particularly on the functions of upper
catchments and their relation to water using systems downstream (10 marks).
2) Discuss the primary hydrological objectives (and the conflicts that may arise) of
agricultural water management at the different scales – farm level, catchment level
and river basin level. Use the concept of closed and open hydrological units (5
marks).
3) Water for irrigation can be harvested in downstream locations in a catchment in
conventional dams, or in many small storage structures upstream for direct local
use in agriculture. Discuss the advantages/disadvantages of collecting surface
runoff at the small scale (farm level, village scale) in the upper catchment (e.g, in
many small water harvesting system), compared to collecting surface runoff at the
larger scale, in the downstream end of a catchment (e.g., in one conventional dam).
Focus on the water resource implications (the amount of runoff collected and the
ease/difficulty to use it), and the environmental implications (5 marks).
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Question 2 PARTICIPATORY CATCHMENT MANAGEMENT (20 marks)
You are responsible for planning water resource use at a catchment level. You are
concerned with runoff generation from different land uses, and the withdrawal of water
by upstream farmers (for irrigation). You know that there is severe land degradation
occuring in the upper catchment, due to over grazing, deforestation and poor
agricultural practices. This is affecting downstream communities through storm surface
runoff causing erosion, and a serious reduction in baseflow (groundwater recharge),
causing water scarcity downstream.
Your task is to (1) map current water use and runoff generation and (2) organise the
community in order to create a forum for common management of water resources
which improves the situation for all – improved livelihoods upstream and secured
water downstream. You are concerned that downstream water users (for agriculture
and for households) do not get enough water, and you are also concerned about a
wetland downstream that is drying out.
Describe in simple terms the steps you would take in carrying out
(1) A survey of current water use and runoff generation (5 marks),
(2) Organise the community for common sharing of water resources (15 marks).
For the mapping (1) think in terms of how you would go about mapping different land
use types and what factors (parameters) you would be most interested in knowing (to
assess runoff generation).
Question 3 SOIL AND WATER BALANCE (20 marks)
You are working in a district development office in a rural area located in a semi-arid
savanna characterised by unreliable rainfall, frequent droughts and dry spells, and
serious soil fertility depletion. People make their living from farming, predominantly
rainfed farming from small plots of land (2 ha cropped land per household on average).
You conduct a survey and are able to assess the following:
Yield levels of maize are low, on average 1 t/ha
Rainfall in the area is 500 mm/season
Surface runoff is high, amounting to on average 20 % of rainfall/season
Water productivity for the maize crop is estimated at 2000 m3/t (m3 of
evapotranspiration per ton of maize).
A doubling of yields would improve water productivity to 1500 m3/t.
From this information, estimate the following:
1) Using the on-farm water balance with its two partitioning points, estimate rainfall
partitioning (into Surface Runoff, Evapotranspiration and Drainage) from the
present data (10 marks).
2) Estimate the same water balance for a situation where soil and water management
improves so that yields double to 2 t/ha. Water productivity would then improve to
1500 m3/t through the reduction of evaporation, and surface runoff would be
reduced to 10 % of rainfall (10 marks).
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Question 4 SOIL AND WATER MANAGEMENT (20 marks)
Agricultural water management at farm level is concerned with two main issues:
1) To maximise plant water availability
2) To maximise plant water uptake capacity
These are directly related to how rainfall is partitioned in the on-farm water balance
(the 2 partitioning points). Also, farmers are concerned with the TEMPORAL aspect of
managing plant water availability and uptake capacity.
Give 2 management examples of each issue above (1) and (2) (10 marks).
Give 1 management example of how to address the TEMPORAL variability of (1) and
(2) (10 marks).
Question 5 INSTREAM FLOW REQUIREMENTS (20 marks)
1) With the aid of a well-illustrated diagram, briefly explain the importance of
different components of a flow regime to a river ecosystem (10 marks).
2) As the project manager tasked with implementing environmental flow
recommendations in the Mazowe catchment, present in sufficient detail the distinct
desirable features of a plan that is likely to lead to successful implementation (10
marks).
Question 6 MANAGING DROUGHTS AND FLOODS (20 marks)
1) Of what importance are the conceptual, operational and disciplinary definitions of
drought to the succinct management of this natural hazard? Provide examples with
each of the definitions (6 marks).
2) While drought is a normal feature of every climate, list any two factors that
significantly increase society’s vulnerability to and risks associated with drought (4
marks).
3) In an endeavor to minimize drought impacts through mitigation and risk
management, which critical constraints does drought management planning need to
take cognisance of and why? Give any five constraints (10 marks).
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