integrated rainwater management strategies: hydrology and hydrological modeling

Integrated Rainwater Management Strategies: Hydrology and Hydrological Modeling

Birhanu Zemadim, Matthew McCartney, Bharat Sharma and Seleshi Bekele

CPWF Nile Project 2: Integrated rainwater management strategies – technologies, institutions and policies

Rationale

For Integrated Rainwater Management Strategies (RMS) want to know: what works, where and why?

This requires basic biophysical understanding: • how much rain falls & where does the water go? • how much water is “used” in different components of the landscape? • what changes will different interventions make? • what are the on-site and downstream impacts of scaling-up the interventions?

Project Activities

Hydro-Meteorological instruments installed in three watersheds to:

• measure rainfall, flow, climate variables, soil moisture & water table •provide insights into hydrological fluxes, processes and water budget

Hydrological modeling to determine: •Rainfall –Runoff relationships•Soil/Vegetation/Livestock water interactions •Water balance and catchment yield•Understanding of flow regime necessary for design of RWH structures •Possible biophysical impacts of scaling-up interventions•Possible biophysical implications of climate change

(Dapo)

(Mizewa)

(Mieja)

Outputs

•Guidance on suitable RMS for the Ethiopian Highlands •Systems for increasing agricultural production using RMS, including a range of water storage options•RMS that maximizes water productivity and ecosystem services

Location of 3 study watersheds

Planned Monitoring

Rainwater management for resilient livelihoods

Contact: [email protected]

mailto:[email protected]

Area27.0 km2

Rice cultivation Trapezoidal pond

Water logging of Maize

Proposed location for flow monitoring

Integrated Rainwater Management Strategies: Hydrometric Monitoring

Mizewa Watershed in Fogera Woreda

Description

· Located in the north-east of the Abbay basin, to the east of Lake Tana

· Tributary to Ribb river

·Rainfall: 1,000 – 1,500 mm

· Large flat floodplain in the vicinity of the lake and hilly catchments to the east

·Traditional diversions and increasingly small pumps used for irrigation

Challenges

· Flooding and water logging

· Drying-up of streams in the dry season and hence water scarcity

· Conflicts between upstream and downstream water users

· Constructed rain water harvesting ponds failing for a variety of reasons

Interventions

· 18 trapezoidal RWH ponds (129m3) lined with geo-membranes have been constructed

· Soil conservation practices: terracing, zai pits, hydro-basins afforestation & protected areas

· 67 new RWH to be constructed by Ag. Bureau




Dapo Watershed in Diga Woreda

Description

· Located in the south-west of the Abbay basin

·Tributary to the Didessa River

·Rainfall: 1,400 – 2,000 mm

·High potential for irrigation

·Currently less than 8% developed by traditional irrigation

Challenges

· Scarcity of water during the dry season

· Long distance (>2 km) to fetch water

· Increasing problems of erosion and loss of soil fertility

· Deforestation and over grazing

· Problems of soil compaction and acidity (on the old Didesa state farm)

Interventions

·Some farmers have built small ponds and reservoirs, but currently there is seemingly little real interest in rain water management

•In some places, Bone, a traditional practice of cultivating in wetland areas using residual moisture, is being undertaken

·There are plans for a 40-60 ha irrigation scheme to commence later this year in the lowlands on the Jirma River

·Feasibility studies are presently being conducted for the establishment of a large irrigation scheme in the lowlands (Didessa River)


Typical view of the Midland

Bridge proposed for flow monitoring

View of the catchment



Meja Watershed in Jeldu Woreda

Description

·Located in the south of the Abbay basin to the north-east of Ambo town

·Tributary to the Guder river

·Rainfall: 1,400 – 2,000 mm

·The headwaters are in a flat wide valley, which is heavily utilized by livestock

·Downstream, the catchment comprises deeply incised mountain streams

·Slopes of up to 80o are being cultivated

·Plantations of eucalyptus occupy approximately 10-15% of the landscape

Challenges

·Seasonal water scarcity

·Heavily deforested in the last 10-20 years

·Slope slumping and gullying are common phenomena

·Productivity has “halved” in recent years (according to local farmer)

Interventions

•Some traditional diversions for irrigating potatoes, maize and onions

•Drainage furrows to remove water from fields in the wet season

•Planting of euclayptus to halt gullying and erosion


Gully with eucalyptus

Middle catchment

Upper catchment

Drainage Traditional bridge


integrated rainwater management strategies: hydrology and hydrological modeling

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