Manica Province, Mozambique

ESTIMATING FIELD-SCALE IRRIGATION WATER AVAILABILITY IN SMALLHOLDER SCHEMES

Overview over Nhamadembe Scheme.

KEY CHALLENGES

Despite progress in the beginning of this decade, poverty reduction in Mozambique has stagnated with 55 percent of the population still living in poverty. In addition, the poverty rate in the rural areas, where two-thirds of the population lives, has been increasing. In the central part of the country, agriculture is dominated by smallholder rain-fed farms which have experienced significant harvest losses as a result of extreme weather like droughts and floods. Promoting sustainable irrigation and drainage is essential in making smallholder farmers resilient to these intensifying climate variations. Acknowledging this, the government of Mozambique has made the development of irrigation a priority for agriculture growth and rural development.

Field irrigation, Nhamandembe Scheme.

NEEDS

Irrigation interventions hold tremendous potential to help farmers cope with increasing climate variability and to ensure food security in many poorer regions of the world. Globally, irrigated land accounts for only 17 percent of total cultivated land, but 40 percent of total food production. Yet, failure to properly manage irrigation schemes often leads to lack of investments in this sector and is the root cause for ineffective and unsustainable water resources management. As the country is heavily increasing its irrigation activities, sound management is required in order to avoid overexploitation of the resources with the corresponding adverse impacts on ecosystems and livelihoods in the downstream alike. 

Empirical research in the field of water management is key in responding to these operational challenges, but has been limited in this context. Therefore, the study ongoing campaign is expected to yield interesting insights in how to use and deploy scalable low-cost methods for scheme-level water balance assessments and for determining how these data can inform locally better irrigation decisions.  

Taking a simple water depth measurement at Nhamandembe Scheme.

IMPLEMENTATION

Together with researchers from IFPRI, a team from the World Bank and specialists from the Ministério de Agricultura, Instituto Nacional de Irrigação as well as from the Eduardo Mondlane University, hydrosolutions ltd. has implemented a low-cost, high-tech, real-time, crowd-sensing approach for measuring field water availability in 3 rehabilitated smallholder irrigation schemes in Manica Province, Mozambique.

Contrary to traditional monitoring approaches that do not scale well due to prohibitive costs and that are prone to vandalism and normally cause significant O&M requirements, the implemented approach relies entirely on local user-reported data that are recorded at specific intervals. All monitoring protocols have been thoroughly discussed with the communities and agreed upon. The designated persons in charge of data collection were recruited from these communities. They were given a contract that clearly specifies their roles and responsibilities with regard to the site- and technology-specific daily data collection and the modalities for remuneration of operational expenses and salaries.

For the small-scale irrigation canals, measurement sites were calibrated using the propeller method for the establishment of stage-discharge relationships. Assuming uniform flow conditions, this allows for translating simple water depth measurements taken by a ruler into discharge values. For sprinklers and hydrants, average yield values were calculated with repeated measurements through volumetric dosing.

The designated data collectors were given a notebook with pre-printed forms to fill out. Data on irrigation canals flows are collected three times daily and averaged over the day. Through the determination of the sub-scheme level catchment of a particular irrigation canal, supplies can be calculated on a per hectare basis on daily scales. For fields that are irrigated by sprinklers and hydrants, the number of active units is recorded twice daily. Multiplying these numbers with average yields, daily water supplies can easily be calculated.

For each scheme, a designated extension officer is collecting the data on a weekly basis and types in the information in a spreadsheet table. The extension officer will also be monitoring the data collection on a weekly basis for QA/QC and follow-up in case of issues/questions and report back to INIR as well as designated university people that are the local project leaders.

Scheme intake measurements compared and precipitation.

RESULTS

When weekly averaged scheme inflows were compared to weekly averaged mean CMORPH precipitation in the region a strong correlation was observed. These preliminary results reveal to which extend inflows are driven by precipitation patterns. Unintentionally, the monitoring campaign captured the failure of the 2015/2016 rains. The associated drought conditions led to hardship in the communities in the province and throughout the whole Southern African region.

Based on these data and concurrent agricultural surveys taken, maps were then created to visualize own and relative water use and productivity (crop per drop) throughout the scheme during the dry season (see Figure). This information tool can be used by water user associations to assess how water may be reallocated to achieve higher yields within the scheme, particularly during the dry season when the resource is most scarce. Evaluations were carried out and findings were communicated to the farmers. It was then evaluated to which extend the feedback tool affects individual farmers’ water use, yields, profits, and yield variability.

Nhamandembe Scheme Map

Mapped Nhamandembe Scheme with gauging sites

Stakeholder briefing on measurement approach in Nhamandembe

Stakeholder discussion for setting up measurement campaign

Calibrating a gauging site along the main canal of Nhamandembe Scheme.

Gauging site calibration, Nhamandembe Scheme, July 2015