Authors: Prof Hans C. Komakech^1,*Paschal Massay¹ Dr Chris de Bont¹

¹The Nelson Mandela African Institution of Science and Technology, Arusha Tanzania

^*email correspondence: hans.komakech@nm-aist.ac.tz

Submitted for: Innovations for Tackling Desertification Webinar – TerraSafe | IDRC | EU, 2025

Theme: Innovations in sustainable water management and land restoration in drylands

Key Insights

• Sand rivers as natural infrastructure: These systems provide a decentralized, renewable, and low-cost water source. With scientific support, their management can be improved to serve multiple water uses in drylands.
• Rainwater harvesting as a complementary solution: Properly designed rainwater harvesting systems such as roadside rainwater harvesting ponds or on-farm storage can reduce pressure on riverbed groundwater, enhance local recharge, and provide critical water during dry spells.
• Locally embedded innovation: Adaptation strategies should leverage existing knowledge and farmer practices. Low-tech and affordable tools (e.g., solar powered hand-dug wells for irrigation, soil moisture conservation) often outperform high-cost infrastructure in these contexts.

Introduction

Desertification continues to pose a major challenge across the drylands of sub-Saharan Africa, affecting agricultural productivity, ecosystem services, water availability and local livelihoods. In Tanzania’s semi-arid regions, particularly the central Dodoma Region, farmers and herders make use of different types of nature-based solutions to increase their resilience to drought. Specifically, they access water stored in the riverbed of ephemeral sand rivers, they enhance natural on-farm depressions to support rice cultivation, and they make use of roadside ponds for domestic, livestock and agricultural purposes. All these innovations also capture run-off during the rainy season, thereby mitigating the land degradation that impacts the area. In spite of their importance for surrounding communities, these innovations remain under-researched and underutilized in development and water policy planning. Researchers and students from the Nelson Mandela African Institution of Science and Technology (NM-AIST) in Arusha, Tanzania, have started studying these different innovations as part of the IDRC/FCDO funded BASIN project, under the CLARE program. In this insight brief we highlight some of the preliminary findings surrounding these technologies. 

Harnessing Subsurface Storage in Sand Rivers

The Bubu Sand River in Dodoma Region is a seasonal watercourse with a sand-filled riverbed that stores large quantities of (very) shallow groundwater. Communities relying on these sand rivers tap into this water using shallow scoop holes or hand-dug wells, especially during the dry season when surface water is unavailable. In Kondoa district, smallholder farmers are using everyday tools (e.g. buckets) to extract water from the riverbed for irrigating crops such as cabbage, leafy vegetables, tomatoes, watermelon and bananas. Some even go further and plant their crop directly within the riverbed. While these techniques support dryland livelihoods, challenges and questions remain. First of all, almost all irrigation is currently done through buckets, using manual labour. This means that only farmers with land directly adjacent to the river can make use of it. Secondly, and linked to the previous point, the carrying capacity of the sand river, and therefore the opportunity for agricultural intensification/expansion, is currently unknown. Finally, the natural dynamics of the river mean that it shifts location, which is a challenge when it comes to making more permanent investments, as agricultural land can become part of the river and vice versa. The research by the BASIN team is aimed at further understanding both the river and its potential uses.

Enhancing natural depressions for rice cultivation

In Chemba district of Dodoma Region, rainfed rice farming in natural depression is emerging as a climate adaptation strategy. Famers are developing small natural ponds to capture and store rainwater for rice cultivation. Although the area per pond is relatively small (approximately 0.05 hectares), most farmers cultivate multiple ponds. Consequently, they can harvest between 10 and 15 bags of paddy rice per acre, which is comparable to the national average of 2.2 tonnes per hectare. This local practice cultivating small natural ponds in arid regions constitutes a nature-based innovation that, when effectively managed, can serve as a buffer to climate variability. However, as more people start clearing bushlands, especially places where water naturally pond after rain events, the fragile dryland ecosystem may become severely degraded.

Roadside ponds for multiple use

Local runoff collection often from roads or compacted surfaces forms temporary ponds during the rainy season. These are used for livestock watering and limited irrigation. With minimal engineering upgrades (e.g., proper embankments, silt traps, and lining), such ponds can be transformed into reliable seasonal water sources that reduce erosion and increase groundwater recharge. This supports both land rehabilitation and community resilience through soil and water conservation.

Conclusion

The threat of desertification continues to undermine livelihoods, food security, and ecosystem integrity across Africa’s drylands. However, this challenge also presents an opportunity: to rethink how we manage water, restore degraded land, and empower communities with nature-based and context-specific solutions. Field research in central Tanzania shows that scalable, low-cost innovations are already supporting livelihoods amidst climate variability. Researchers and practitioners must work together to sustainably scale up these innovations and increase their effectiveness in contributing to water security and preventing further degradation of the environment.