IWRA Proceedings

Introduction

It is expected that use of groundwater for local-scale irrigation will increase significantly across sub-Saharan Africa, with corresponding increase of stress on coupled groundwater and surface water resources (Villholth, 2013). This will make them more vulnerable to climatic variability, as well as increasing inequity of access to the resource and presenting challenges to existing governance arrangements which are often weak or inadequate. Although previous studies have been carried out into large scale resource assessments, there is a scarcity of data available on how large scale assessments relate to the reality of the experience of local communities. We present new groundwater level data from shallow hand-dug wells monitored by local communities, and a methodology that can link larger scale assessments with local scale hydrological behaviour, as a step towards developing methods and tools to support local scale adaptive management of shallow groundwater resources as their use increases.

Methods

This paper describes water resource assessments at both larger catchment and local community scales, using a combination of data sources including participatory monitoring of groundwater, surface water and rainfall by community observers, together with field hydrogeological studies and spatial hydrological modelling. The study is part of a wider methodological framework that also includes social assessments of the potential and constraints for livelihood improvement, technical feasibility, and governance frameworks for long-term development.

The study area is a community-level administrative district, the Dongila woreda, in the Amhara region of Ethiopia with an area of about 800 km2, with specific focus on the Dangeshta kebele with an area of about 40 km2 as the community scale at which water management decisions are made. This study focusses on the 660 km2 Kilti catchment, a tributary of the Gilgel Abay, a tributary of the Abay (Blue Nile) upstream of Lake Tana.

Hydrological modelling studies were carried out at the catchment scale using the Shetran integrated groundwater-surface water model (Ewen et al., 2000), using large scale data from national hydrometric networks, TRMM remote sensing products, and global climate model reanalysis data. The catchment model has been calibrated against long-term historical baseflow and total flow data as well as the initial local groundwater measurements (Parkin et al., submitted). We have now disaggregated the spatial information from this model, also using detailed field hydrogeological analyses and spatial climatic data, to provide understanding of water balance components at the local scale at which management of shallow groundwater resources for local-scale irrigation is necessary.

Results and discussion

We have found that monitoring by community observers can provide good quality measurements of key hydrometric variables to support integrated groundwater and surface water modelling. The spatial modelling studies have provided consistent representations of hydrological responses at scales from less than 1 km2 to more than 600 km2. The groundwater and surface water responses showed behaviour consistent with understanding gained from the initial field hydrogeological survey, for example in the extent of the ephemeral river channels in the dry season.

We derive local scale water balances from the spatial representation of the Kilti catchment. A simple water balance model is then constructed for representative local areas, including sub-catchments, and administrative management units, to represent the main surface and subsurface flow components. We show how local water budgets change with the hydrogeological characterisation, and demonstrate the resilience of local areas to climatic variability. These local models depend on the data monitored by the local communities, and we outline how the co-production of knowledge from this citizen science approach can support an approach that is updated as new monitored data becomes available, and is therefore a key step towards development of tools for local adaptive management of shallow groundwater resources.

Conclusions

Our studies have demonstrated the application of a methodology to provide understanding of shallow groundwater and surface water resources at the local scale consistent with available hydrometeorological information at larger catchment scales. The focus of the study is at the scale at which community-led resource management is necessary for development of local scale irrigation, which is predicted to increase significantly in sub-Saharan Africa in the near future. We have demonstrated that community-led monitoring of groundwater levels, stream levels, and rainfall can provide valuable quantitative information at the local scale which complements available larger scale data, and that this local scale of monitoring and characterisation is necessary for adaptive management of available groundwater and surface water resources at local scales.

Ewen, J., Parkin, G. and O'Connell, P.E., 2000. SHETRAN: distributed river basin flow and transport modeling system. ASCE J. Hydrologic Eng., 5, 250-258.

Parkin, G. et al. (submitted). Modelling and community monitoring for adaptive shallow groundwater management in Africa. Ground Water.

Villholth K.G. (2013) Groundwater irrigation for smallholders in Sub-Saharan Africa -- a synthesis of current knowledge to guide sustainable outcomes, Water International 38 (4) 369-391.