Comparison Assessment of Water Use and Damage between Modern and Traditional Rice Irrigation Schemes: Case of Usangu Basin, Tanzania

Abstract

Water management and competition between users in water scarce river basins is a major challenge facing the human race. The inter dependence of users in such basins, necessitates a clear understanding of each user in relation to the location, the water demand, and the duration of water need. The understanding of these factors, together, is very important for the management of water resources in such basins without which, it is argued that, water is overused and wasted. As an example of this, the large modern and improved rice irrigation systems in Tanzania are believed to use water more efficient than the traditional irrigation systems. Yet, well-founded scientific analyses are a necessary part to quantify such beliefs as they can inform us whether the natural resource, in such systems, is properly utilized and managed or not. Likewise, such studies can allow us to quantify how much water is over used and thus the natural resource is unnecessarily degraded. This paper explores a study conducted in the Usangu basin, Tanzania, to investigate the gross and net needs for modern and traditional rice irrigation schemes, and the implications with regards to water resource management and damage. Problems relating to modernization of traditional smallholder irrigation systems and upstream - downstream water users are further discussed. The paper concludes from the study that modern irrigation schemes are inefficient compared to traditional irrigation schemes. Also modernization of traditional schemes in the study area have resulted into over abstraction and reduced productivity of water. Looking to the future, this study tells us that improvement or modernization of irrigation infrastructure should be balanced between negative impacts to available water resources albeit it’s significant economic contribution to the community.

Soil fertility and land sustainability in Usangu Basin-Tanzania

“…Where Igalako, Mahongole, Kapunga, and Ihahi observed high P concentrations, i.e., 22.1, 40.32, 21.5, and 49.85 mg/kg, respectively ( Figure 3 b and Table 4 ). These schemes are located in lowland areas of the Usangu agro-ecosystem receiving runoffs from the upper parts of the Usangu basin and are among schemes that are highly intensified ( Machibya and Mdemu, 2005 ; Ngailo et al., 2016 ). The remaining schemes such as Mubuyuni, Isenyela, Ilaji, Chimala, Uturo, and Mabadaga ( Figure 3 b and Table 4 ), had low P concentration as these are smallholder farmers schemes with less fertilizer input and no or very low manure applications.…”

Linking key environmental stressors with the delivery of provisioning ecosystem services in the freshwaters of southern Africa

“…The direct utilisation of water resources, by way of water abstraction or diversion, can play a substantial role in degrading downstream provisioning ecosystem services. Irrigation has historically been the primary recipient of such diverted supplies in Africa, comprising 80% of all water abstractions (Machibya and Mdemu ). While irrigated agriculture can drive significant socio‐economic development in rural communities, downstream users can be negatively impacted, if they are disenfranchised from the upstream irrigation scheme, or depend on the system's natural, pre‐abstraction hydrology to receive the ecosystem services (Oosterbaan ).…”

“…While irrigated agriculture can drive significant socio‐economic development in rural communities, downstream users can be negatively impacted, if they are disenfranchised from the upstream irrigation scheme, or depend on the system's natural, pre‐abstraction hydrology to receive the ecosystem services (Oosterbaan ). For example, a government scheme to upgrade traditional rice paddy irrigation infrastructure in the Usanga Basin, Tanzania resulted in an inequitable allocation of water resources favouring upstream users at the expense of downstream users (Machibya and Mdemu ). While many forms of water utilisation infrastructure exist, it is the construction of on‐channel dams, a major consequence of agricultural intensification and urban expansion throughout southern Africa, which has had the most widely documented negative impact on downstream services.…”

Analysis of seasonal land use in Usangu wetlands, Tanzania: an object-oriented technique for multi-temporal analysis with high-resolution data

“…The Usangu wetlands (figure 1) are located in the upper Ruaha Basin in southwest Tanzania, roughly between 7 41 0 and 9 25 0 S and 33 40 0 and 35 40 0 E. This is the upper catchment of the Rufiji River, and contains several important tributaries: the Mbarali, Kimani, Ruaha, Chimala, Mkoji and Ndembera (Machibya and Mdemu 2005). The basin covers approximately 20 800 km 2 and supports a population of 200 000 people who are mainly farmers, herders, fishermen and users of natural (wetland) resources.…”