W A T E R Water Harvesting: A Namibian Flood Mitigation Oshanas

AUTHOR: Hannah Brendell PolicySpecialist-Intern@RDJConsulting

Not a new matter but definitely a crucial matter, in the March Briefing of 2022, we looked at flood control through the use of remote sensing in north-eastern and north-central areas of Namibia. Remote sensing allows Namibian officials and municipalities to receive advanced warnings of flooding and in turn properly prepare

Despite the usefulness of remote sensing in flood awareness and notification, it is but one of the strategies that can be employed when it comes to preventing some of the negative impacts of floods. What else can be done to help mitigate flooding? The answer just might be Flood Water Harvesting which we will be exploring in this edition

Flood Water Harvesting (FloodWH) “is a method of informal irrigation using the floodwaters of a normally dry water course or riverbed” like with the Oshanas in Northern Namibia According to the Economic and Social Commission for Western Asia (ESCWA) There are generally two (2) types of Flood Water Harvesting namely, floodwater harvesting within streambeds, where turbulent channel flow is collected and spread through [area] where the crops are planted; flood water diversion, where the floods - or spatesfrom the seasonal rivers are diverted into adjacent embanked fields for direct application ”

As seen with the flooding in Northern Namibia once again in mid-January and February this year (2023), the country is flood prone The recent floods resulted in significant problems such as the destruction of property, displacement, school closures, and the destruction of crops

Flood Water Harvesting has already been introduced in Namibia through various pilot projects such as the German-Namibian research project, led by the Institute for Social-Ecological Research (ISOE) titled CuveWaters project and implemented in 2012 in Iipopo, a village in the Oshana region of Namibia before being handed over to the Namibian Government in 2015. The project aimed to redirect flood waters by motor pumping water from Oshanas during the peak rainy season which would then be stored in nearby reservoirs

CuveWaters summarised the communal approach to floodwater harvesting like this:

“The pilot plant for the storage of Oshana floodwater is a combination of different storage options (see figure below) It consists of an underground tank and two ponds, one with a shade net roof and one covered by corrugated iron

The pilot plant has a total storage capacity of 400 m³. The water is intended to be used for irrigation purposes in the greenhouse and in an open garden area. Market-ready vegetables can be grown inside the greenhouse, since the plants are protected from direct sunlight, wind, and pests ”

Developments like these, if explored further, implemented and maintained have the potential to reduce flooding, while improving water availability, providing sustainable jobs in the agricultural industry for peopleconsistentlynegativelyimpactedbyfloods

The Namibian government has recently pledged to develop and rehabilitate several earth dams valued at approximately N$ 98 million (USD 5 5 million) in northern flooding hotspots such as in the Ohangwena, Omusati, Oshikoto, Kavango East and Kavango West regions. Earth dams would capture and store rainwater which would not only reduce flooding but would also help address water shortages in times of drought, which Namibia is also proneto.

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Readings:

https://www cuvecom org/the-river-basin/ https://www unescwa org/sd-glossary/flood-water-harvestingfloodwater-harvesting https://www afrik21 africa/en/namibia-5-5m-for-earth-dams-toaddress-flooding-in-the-north/ https://www.britannica.com/technology/levee https://www aboutmechanics com/what-is-an-earth-dam htm http://www cuvewaters net/fileadmin/edit/Downloads/Publication s/CuveWaters-Factsheet-FWH-2015.pdf https://www geo fuberlin de/en/v/iwrm/Implementation/technical measures/Waterharvesting-techniques/floodwater harvesting/index html https://www namibian com na/153036/archive-read/Germanexperts-help-harvest-floodwaters https://www worldsaid com/node/1773#:~:text=The%20southeaste rn%20parts%20of%20Angola,in%20Ondjiva%20and%20surroundin g%20areas