UNIVERSITY OF SOUTH AFRICA (UNISA)
College of Science, Engineering and Technology
⋄ ⋄ ⋄
WDP4801
Water and Dam Engineering
Semester 1 | Assignment 1 | 2026
⋄ ⋄ ⋄
Assignment Details
WDP4801
Module Code:
Water and Dam Engineering
Module Name:
Semester 1, Assignment 1
Assignment:
2026
Year:
100 Marks
Total Marks:
5 Questions
Questions:
Submitted in partial fulfilment of the requirements for WDP4801 · University of South Africa · 2026
,UNISA | WDP4801 Water and Dam Engineering
Contents
1 Question 1 [15 marks]: Feasibility Study for a Small to Medium-Sized Earth-
fill Dam 4
Question 1: Feasibility Study for an Earthfill Dam 4
1.1 1(a) Primary and Secondary Purposes of the Proposed Dam in the South African
Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 1(b) Why a Dam is Preferred Over Groundwater Abstraction, Water Reuse, or De-
salination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Question 2 [20 marks]: Site Selection and Valley Geometry 8
Question 2: Site Selection and Valley Geometry 8
2.1 2(a) Five Key Site Selection Criteria for Dam Construction . . . . . . . . . . . . 8
2.2 2(b) How Valley Shape and Topography Influence Storage Capacity, Dam Type,
and Construction Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 Question 3 [20 marks]: Geological Investigations and Foundation Conditions 14
Question 3: Geological Investigations and Foundation Conditions 14
3.1 3(a) Geological and Geotechnical Investigations Required Before Dam Construc-
tion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 3(b) How Foundation Conditions Influence the Choice of Dam Type . . . . . . . 16
4 Question 4 [25 marks]: Hydrology, Sedimentation, and Assurance of Supply 19
Question 4: Hydrology, Sedimentation, and Assurance of Supply 19
4.1 4(a) The Importance of Mean Annual Runoff (MAR) in Reservoir Sizing . . . . 19
4.2 4(b) Impact of Evaporation, Sedimentation, and Assurance of Supply . . . . . . 20
Page 2 of 29
,UNISA | WDP4801 Water and Dam Engineering
5 Question 5 [20 marks]: Cost Components and Risk Management 23
Question 5: Cost Components and Risk Management 23
5.1 5(a) Major Cost Components of Dam Construction . . . . . . . . . . . . . . . . 23
5.2 5(b) Three Major Risks in South African Dam Development and Mitigation Mea-
sures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Reference List 28
Page 3 of 29
, UNISA | WDP4801 Water and Dam Engineering
Question 1 [15 marks]: Feasibility Study for a Small to Medium-Sized Earth-
fill Dam
Your local municipality is considering the construction of a small to medium-sized earthfill dam
to augment water supply for domestic use and emerging irrigation schemes. You have been
appointed as an engineering technologist to conduct a preliminary feasibility study.
1(a) Primary and Secondary Purposes of the Proposed Dam in the South African Con-
text
Primary Purpose
The primary purpose of the proposed dam is domestic water supply augmentation. South
Africa is classified as a water-scarce country, with mean annual rainfall of approximately 497
mm compared to the world average of 860 mm (Department of Water and Sanitation, 2018).
Many municipalities, particularly in semi-arid regions such as the Karoo, Limpopo, and parts
of the Eastern Cape, rely on surface water impoundment to meet the basic needs of their com-
munities.
The dam will capture surface runoff during rainfall events and store it for controlled release
throughout the year. Under the National Water Act 36 of 1998, local authorities have a duty
to ensure a reliable basic water supply of at least 25 litres per person per day within 200 me-
tres of every household (DWAF, 2004). A dam serves this function by creating a buffer against
seasonal variability in streamflow, which is characteristic of South African rivers.
Secondary Purpose
The secondary purpose stated in the question is support for emerging irrigation schemes.
Many smallholder and emerging farmers in peri-urban and rural South Africa lack reliable ac-
cess to water for food production. A dam can supply irrigation water for vegetables, dryland
crops, and small livestock operations, contributing to food security and rural economic devel-
opment (Van der Zaag & Savenije, 2014).
Additional secondary purposes commonly associated with small to medium dams in South
Africa include:
Page 4 of 29
College of Science, Engineering and Technology
⋄ ⋄ ⋄
WDP4801
Water and Dam Engineering
Semester 1 | Assignment 1 | 2026
⋄ ⋄ ⋄
Assignment Details
WDP4801
Module Code:
Water and Dam Engineering
Module Name:
Semester 1, Assignment 1
Assignment:
2026
Year:
100 Marks
Total Marks:
5 Questions
Questions:
Submitted in partial fulfilment of the requirements for WDP4801 · University of South Africa · 2026
,UNISA | WDP4801 Water and Dam Engineering
Contents
1 Question 1 [15 marks]: Feasibility Study for a Small to Medium-Sized Earth-
fill Dam 4
Question 1: Feasibility Study for an Earthfill Dam 4
1.1 1(a) Primary and Secondary Purposes of the Proposed Dam in the South African
Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 1(b) Why a Dam is Preferred Over Groundwater Abstraction, Water Reuse, or De-
salination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Question 2 [20 marks]: Site Selection and Valley Geometry 8
Question 2: Site Selection and Valley Geometry 8
2.1 2(a) Five Key Site Selection Criteria for Dam Construction . . . . . . . . . . . . 8
2.2 2(b) How Valley Shape and Topography Influence Storage Capacity, Dam Type,
and Construction Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 Question 3 [20 marks]: Geological Investigations and Foundation Conditions 14
Question 3: Geological Investigations and Foundation Conditions 14
3.1 3(a) Geological and Geotechnical Investigations Required Before Dam Construc-
tion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 3(b) How Foundation Conditions Influence the Choice of Dam Type . . . . . . . 16
4 Question 4 [25 marks]: Hydrology, Sedimentation, and Assurance of Supply 19
Question 4: Hydrology, Sedimentation, and Assurance of Supply 19
4.1 4(a) The Importance of Mean Annual Runoff (MAR) in Reservoir Sizing . . . . 19
4.2 4(b) Impact of Evaporation, Sedimentation, and Assurance of Supply . . . . . . 20
Page 2 of 29
,UNISA | WDP4801 Water and Dam Engineering
5 Question 5 [20 marks]: Cost Components and Risk Management 23
Question 5: Cost Components and Risk Management 23
5.1 5(a) Major Cost Components of Dam Construction . . . . . . . . . . . . . . . . 23
5.2 5(b) Three Major Risks in South African Dam Development and Mitigation Mea-
sures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Reference List 28
Page 3 of 29
, UNISA | WDP4801 Water and Dam Engineering
Question 1 [15 marks]: Feasibility Study for a Small to Medium-Sized Earth-
fill Dam
Your local municipality is considering the construction of a small to medium-sized earthfill dam
to augment water supply for domestic use and emerging irrigation schemes. You have been
appointed as an engineering technologist to conduct a preliminary feasibility study.
1(a) Primary and Secondary Purposes of the Proposed Dam in the South African Con-
text
Primary Purpose
The primary purpose of the proposed dam is domestic water supply augmentation. South
Africa is classified as a water-scarce country, with mean annual rainfall of approximately 497
mm compared to the world average of 860 mm (Department of Water and Sanitation, 2018).
Many municipalities, particularly in semi-arid regions such as the Karoo, Limpopo, and parts
of the Eastern Cape, rely on surface water impoundment to meet the basic needs of their com-
munities.
The dam will capture surface runoff during rainfall events and store it for controlled release
throughout the year. Under the National Water Act 36 of 1998, local authorities have a duty
to ensure a reliable basic water supply of at least 25 litres per person per day within 200 me-
tres of every household (DWAF, 2004). A dam serves this function by creating a buffer against
seasonal variability in streamflow, which is characteristic of South African rivers.
Secondary Purpose
The secondary purpose stated in the question is support for emerging irrigation schemes.
Many smallholder and emerging farmers in peri-urban and rural South Africa lack reliable ac-
cess to water for food production. A dam can supply irrigation water for vegetables, dryland
crops, and small livestock operations, contributing to food security and rural economic devel-
opment (Van der Zaag & Savenije, 2014).
Additional secondary purposes commonly associated with small to medium dams in South
Africa include:
Page 4 of 29
