An analysis of water demand and quality within the Iishana-system, Namibia
No Thumbnail Available
Date
2025
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Namibia
Abstract
The Namibian people, particularly those living within the Iishana system, which is a
subset of the Cuvelai Basin, often encounter recurrent floods and droughts. After each
rainy season, the Iishana system dries up gradually, hence, water for both agricultural and
potable purposes becomes crucial. To enhance water availability, this study evaluated
water demand and quality within the Namibian Iishana system, considering planned
infrastructure developments and the rehabilitation of existing systems. This study
employed a physical interaction, as well as the administration of questionnaires, to
determine the population per-capita demand within the Iishana system. A thirty-year
population projection was used to estimate future water demand. Moreover, the
hydrological data (daily rainfall and temperature) from 2012-2021 were incorporated. As
the water quantity and quality are inseparable, ten water samples were collected for Water
Quality Index (WQI) and Multivariate Statistical Analysis using Minitab (21.2). The Piper
diagram generated using Grapher (20.2.321) further classified water types. The current
rural population and livestock water demand were estimated to be 2,479 and 4,282
m3
/respectively. Projected demand forecasts for 2033 (0.9 Mm3
/year), 2043 (0.5
Mm3
/year), and 2053 (0.1 Mm3
/year) indicate a declining trend, due to outmigration. More
so, water availability is found to be affected by climate change, making it insufficient to
meet demand. Climate data analysis showed a rising temperature trend, with annual
precipitation (310 mm) far exceeded by evaporation (2,500 mm), resulting in water level
drops and poor quality. The WQI scores (81.30-320.65) classified the water as unsuitable
for human consumption. The Principal Component Analysis (APA) identified key
influences: soil formation, mineral dissolution, microorganisms, and agricultural runoff.
The Piper diagram classified 100 % of the sampled water as Na+
-K
+ water types,
indicating salinisation. The water crisis in the area demands urgent, coordinated action to
balance supply enhancement with quality control. Therefore, it is crucial to harvest flood
and rainwater by expanding the size of natural pans in the study area for use during dry
periods. Water treatment for pans can augment the water supply for the rural population
Description
A thesis submitted in fulfilment of the requirements for the degree of masters of science in Civil Engineering
Keywords
Per capita demand, Rural population, Iishana system, Water demand, Water supply, Infrastructure, Water quality, Namibia, University of Namibia