Themi River Catchment, Pangani River Basin, Tanzania
OPERATIONAL RIVER DISCHARGE MONITORING
The Themi River sub-catchment is part of the larger Pangani River Basin in north-western Tanzania. The sub-catchment covers a total area of 363 square kilometres containing a diverse range of climatic zones along the slopes of Mt. Meru and in the vicinity of the strongly expanding city of Arusha. Especially in the semi-arid to arid downstream, the water demand is over-exponentially growing due to the ever increasing irrigation agriculture activities there. Combined with increasing water abstractions and pollution by the city of Arusha, this is repeatedly leading to serious conflicts and tensions in the catchment.
Currently, the Pangani Basin Water Office (PBWO) does not maintain gauging sites in the increasingly stressed subcatchment. It has neither developed an abstraction policy that takes sustainability constraints into account nor is it able to properly enforce the issuance of abstraction permits and the collection of irrigation fees.
River committees (RC) have emerged in the Themi catchment as local non-governmental decision making structures to coordinate water demand between different water users (small scale farmers, large commercial farmers and municipalities) sharing the same water source. The RC form part of the Upper Kikuletwa Water User Association.
Many of the RC traditionally used a wooden stick with different markers to measure water depth at canal intakes for the purpose of inter-community compliance monitoring and water-allocation. The elders introduced the bamboo-stick around 1960 as increasing livestock and farming had let to serious conflicts in the area. Without knowing the exact discharge but the water level at a particular location, the responsible elders could derive if the conveyed water would be enough for the respective water-user group by experience. During water shortage all communities are obliged to lower the water-level at their intake to agreed levels. During extreme shortage all furrows have to close their intake structures. Interestingly, the water-level was never converted to volumetric discharge and neither submitted to the basin authorities but used by the river committee internally.
The RC employ water guards to control abstraction points along the river and its tributaries. These guards are paid from by control fees from each furrow. Even though the each furrow should pay a volumetric fee for the water it abstracts, flat rate pricing is the current practice in the basin as abstraction volumes are not monitored. The PBWO is in fact struggling already with the recovery of the abstraction permits as the upstream communities tell the officers that they are not willing to pay for water which, so far, was free while the downstream irrigators deny payments on the grounds that upstream communities are not paying either. Like this, the irrigation communities are interlocked in a game of chicken where the one players choice depends on what the other player is doing.
The PBWO requested the iMoMo team to test deploy selected scalable low-cost and high-tech technologies for measuring river discharge and intakes at selected locations. The trial was carried out over several years and support by the Upper Kikuletwa Water User Organization.
Based on the request by the PBWO, the iMoMo team started to co-design a monitoring campaign strategy in the Themi River together with local stakeholders.
For data acquisition, the simple traditional stick was the consortium's point of departure for the development of a new water measuring device that would a) measure depth through a pressure sensor, b) display the value and c) would allow the measurements to be uploaded to a database, either manually via SMS or automatically with a dedicated Smartphone application. The low-cost, high-tech device was welcomed by communities as it provided an object reading of the furrow water depth directly displayed on the SmartStick.
From a water balance perspective, reading only water levels is clearly not enough. Therefore, the selected members from the up- and downstream communities were trained in data collection using the smartphone-based discharge.ch technology.
The disconnect between PBWO and individual stakeholders in the river catchment led to the creation of a so-called Service Center that was housed inside the MoW premises in Arusha. The Service Center was staffed with two local experts from the region. The Service Center monitored the data collection activities by the communities on a regular basis and collected operational feedback at the same time.
5 points were monitored along the Themi River off-farm and 19 furrow intakes were monitored over a period of 2 years through local involvement. Each crowd-senser and the larger communities could further subscribe to an SMS-based weather forecast service and sign up for the receipt of information of the latest crop prices at nearby markets. For each community member involved in the collection of data, either on- or off-farm, contracts were signed that clearly specified the terms and conditions of the monitoring protocol and guaranteed a compensation of operational expenses. The PBWO was given access to the crowd-sensed data collected via a web-based interface to the cloud-based database where the data was stored.
The non-traditional data collected in the Themi River Basin allowed the PBWO to monitor river discharge as well as selected furrow intakes in the basin. The discharge.ch technology was further implemented in selected official gauging sites in the larger Pangani to modernize the data collection and transmission process from the point of measurement to when data are managed and analyzed in the PBWO.