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United Nations Environment Programme
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Newsletter and Technical Publications
Freshwater Management Series No. 5

Guidelines for the Integrated Management of the Watershed
- Phytotechnology and Ecohydrology -


Africa

The cities of Cape Town, South Africa, and Harare, Zimbabwe, differ in many ways - not the least of which is in their climatic characteristics, with Cape Town having a mediterranean climate and Harare a sub-tropical semi-arid climate. These differences affect the timing and intensity of precipitation and runoff events in different ways. However, both cities share similar concerns over their water resources and water supplies, and, hence, both cities have utilised ecohydrological principles in their efforts to protect and manage their limited water resources.

During the 1980s, the City of Cape Town was experiencing rapid urban growth, with concomitant pressures upon the natural environment. These pressures were manifested in degraded waterways and shoreland vegetation. In addition, the rapid expansion of the City was resulting in development in marginal areas, prone to flooding, which raised public health concerns. The City staff responded to these issues using hard engineering approaches and traditional park management measures that were soon overwhelmed by the scale of urban development and development-related impacts. Further, City resources and staff were being hard pressed to maintain a consistently high level of service throughout the City and consideration was given to seeking assistance from a variety of community groups and neighbourhood associations. Initially, staff were hesitant to actively involve these groups as previous experiences, based upon the assumption that such community groups would help to maintain their environment, had proven less than successful.

In an attempt to resolve this conflict, a series of meetings between the City officials –councillors and staff - and City residents across the spectrum of economic condition were convened to identify issues of concern and the means to overcome these concerns. During the course of these meetings, citizens expressed their concerns that the previous City programs had not considered the needs and concerns of the community in implementing the programme. One example was the planting of trees at such regular intervals as to obstruct doorways and driveways, impeding access to properties and often creating public safety hazards by providing shelter for criminals intent to robbing passers-by. Other concerns related to the choice of plants (mainly exotics requiring an high degree of maintenance) and the management of solid waste that resulted in large areas that were poorly vegetated and prone to litter.

To better address this deteriorating quality of life, the City implemented a programme known as the "Greening of the City" project. A key element of this project was based upon the restoration and maintenance of the City’s public open spaces and parklands, including river corridors and coastal lakes (see Thornton et al. 1995). Integral to this project was the planting of trees and control of nonnative invasive species, including various eucalypts and acacias that had historically been imported into the region from Europe and Australia, by developing public-private partnerships between the City and the community. These efforts included the following types of actions:

  • Use of public monies to protect wetland resources.
  • Dechannelisation of flood control drainageways to reinstate the wetlands as important elements in the natural hydrology of the City and surrounding region.
  • Contribution of time, effort, and funds by community members and individuals in, inter alia, the removal of refuse from waterways and wetlands, etc.
  • Support from the business sector in the form of sponsorships for both awareness-building programmes and activities within the community, such as the refuse removal activities mentioned above.

The culmination of these actions was a series of "River Days" based around such themes as "the river in your community" which helped to not only inform students and citizens of the need to implement "good housekeeping" practices within their own homesteads but also work together as a community to improve their own immediate surroundings. Good housekeeping hints included information on the proper and safe disposal of household chemicals, appropriate rates and types of fertilisation for gardens, lawns and flower beds, and ways and means of conserving water, among other ideas. Contests, radio spots, and other informational pathways were used to encourage individuals to adopt a more environmentally-friendly lifestyle, which is the key to sustainable economic development in local communities.

In Harare, during the 1970s, the then ongoing liberation struggle was resulting in unique pressures upon communities and their aquatic resources. Notwithstanding, the government had embarked upon effective programmes for water quality management, utilising, in part, ecohydrological principles that included greenways and riverine buffer lands. As was demonstrated during the City of Cape Town programme described above, an effort was made to reach local community members with appropriate informational programming, and to provide local communities with basic sanitation services to minimise the discharge of contaminants into the environment. As shown by the rehabilitation of Lake Chivero (formerly Lake McIlwaine, see Thornton 1982), these programs were effective in mitigating the eutrophication of the major water supply impoundments by controlling both point source and nonpoint source pollution of these systems. Subsequently, and perhaps consequently, ongoing urban development in the catchment has unfortunately negated many of these improvements as greater numbers of people were displaced from rural areas and migrated to the City. Following independence, this trend continued, with the result that the semi-formal settlements at the headwaters of Lake Chivero became formalised as a city of equal size to Harare. In this situation, the environmental imperatives were over-ridden by economic necessity and public safety concerns, underlining the critical importance of including both ecological and socio-economic considerations in integrated catchment management.

Latin America

The Bermejo River is a major tributary stream to the Plata River, draining portions of southern Bolivia and northern Argentina. The Bermejo River basin was identified as the largest single contributor of sediment to the Plata River and its estuary. Consequently, the Bermejo River basin, although a small part of the overall Plata River basin, had a significant impact on the ability of maritime traffic to navigate the Plata River between Buenos Aires and Resistencia/Corrientes. The sediment load also has a significant impact of the riverine ecosystem.

During the mid-1990s, under the auspices of the Global Environment Facility (GEF), the United Nations Environment Programme (UNEP) and General Secretariat of the Organization of American States (OAS) implemented a major basin planning programme within this tributary system with the objective of identifying the causes and consequences of soil loss in the basin and measures applicable to its control. Included within this planning program were pilot demonstration projects that implemented phytotechnological principles for the reduction in sediment losses and the consequences of changes in riverine morphometry. These projects included three different programmes that were proven to be successful in mitigating the consequences of human disturbances of the hydrological system and of the landscape. The lessons learned from these pilot studies are currently being replicated within the basin. Each of the demonstration projects and the specific applications utilised in the mitigation of human disturbances is briefly described below.

In the Upper Bermejo River basin, nestled in the rain shadow of the Andes Mountains, is the municipality of Tarija. This town and associated rural district is an agrarian area, historically based upon livestock rearing and small holdings. Few fences meant that the sheep and goats had relatively free range through the basin, which is characterised by extremely friable soils and periodic, episodic rainfall events that have created such extreme erosion gullies that the area has been likened to a moonscape. Erosion gullies, once created, often extended backward into the landscape, creating erosion features estimated at over 100 metres in height. Compounding this situation was the demand for fuelwood, which further diminished the extent of natural vegetative land cover. Using funds made available through the GEF, UNEP and the OAS partnered with the departmental government and a local nongovernmental organisation (NGO), Viva Verde, to encourage construction of erosion control structures, fencing of pastures, and revegetation of the catchment.

The departmental government worked with the local communities to build a large number of erosion control structures, ranging from small timbered structures within incipient gullies to gabion dikes to earthen retention structures, as a means of limiting downstream transport of soils. While the timbered structures were only marginally successful, being subject to undercutting and bypassing of flood flows, the gabion and earthen structures proved to be durable and robust enough to withstand the extreme variations in flow. The several larger earthen structures also had the unexpected side effect of retaining water that could be used to enhance limited irrigated agriculture in their immediate vicinity. The combination of available water and fenced fields encouraged local farmers, working with the NGO, to diversify their plantings. This had the effect of not only increasing vegetative land cover, but also of improving the local diet by increasing the variety of vegetables available for local consumption.

In similar vein, the project partnered with the local university extension program in the middle portion of the Bermejo River basin to reduce the frequency of slash-and-burn agriculture in this more humid area of the catchment. Although previous efforts by the German Agency for Technical Cooperation at reforestation of disturbed lands had proven unsuccessful, the university staff were certain that a means could be identified that not only would encourage revegetation of the catchment but also contribute to a more established agricultural base. Using only limited funds provided through the GEF, these academics partnered with the local community to develop a basis for terraced agriculture. By providing local farmers with the knowledge necessary to plant and grow fruit trees - that produced a saleable agricultural product - the university extension educators encouraged terracing, composting, and development of an irrigation system that used a portion of the available overland flow for irrigation by one, small segment of the community. This programme proved so successful that a training institute was established in the municipality within which the project was executed. The municipal government, in addition, established a plant nursery to provide fruit trees and vegetable seedlings to persons participating in this project, and the provincial government instituted a revolving loan fund to provide start-up capital for the agricultural and related ventures. The community members built the irrigation system, and provided the ingenuity and initiative to make this demonstration project a success. Not only was the slash-and-burn agriculture controlled, but the diversity of crops and increased level of community income created an improved economic and social climate in this portion of the basin.

In the lower Bermejo River basin, the concerns included both deforestation, which affected the indigenous riparian forests, as well as the invasion of the grassland of the Chaco plains by non-native acacias that benefited from the altered hydrological conditions within the floodplains of the Bermejo River that were consequent to the building of all weather roadways and railways that modified the annual flooding cycle. In the first instance, the provincial governments developed and implemented community school-based curricula that included not only classroom-based educational programmes on the importance of maintaining woodlands as a landscape feature, but also incorporated hands-on learning in the form of growing and rearing tree seedlings. The success of this programme was evident not only in the extent to which communities embraced the curriculum but also by the manner in which the entire community embraced the programme, to the extent that whole families participated in the planting of seedlings and the growing of forested trees. These trees will provide a legacy for these families and their children as the plantations replace trees harvested for fuelwood and other timber products based upon native tree species.

In contrast to the programmes that encouraged maintenance and restoration of native woodlands and grasslands, the control of "vinal" was aimed at the removal of an invasive tree species that was overtaking the native grasslands of the lower Bermejo River basin. These trees thrived in the open lands of the lower Bermejo River floodplain once the extent of the floods was diminished by draining of lands and construction of road and rail ways that effectively created a system of dikes and levees throughout the lower reaches of the river system. The elimination of seasonal flooding provided the perfect opportunity for the invasive acacias to colonise the rich soils of the former floodplain. The Argentine federal agricultural research agency, using funds provided through the GEF-funded project, constructed a series of fords and culverts that allowed the floodwaters of the Bermejo River to, once again, reach areas of the basin from which they had previously been excluded. Restoration of the annual flooding cycle was shown to effectively "drown" the vinal and promote resurgence of the native grasses. While the periodic flooding meant that the ability of local ranchers to graze cattle in certain paddocks was restricted, the flooding effectively controlled the vinal that was reducing the area of available grazing land. By controlling the numbers of fields subjected to this seasonal flooding, the ranchers could not only maintain their grazing herds, but also promote regrowth of the grasslands upon which the herds depended.

Curiously, each of these demonstration projects has implemented phytotechnologies that have accomplished a positive economic benefit within the communities participating in these projects. In addition, the projects have improved the economic base of the communities, public health and well-being, and contributed to the maintenance of the natural hydrological system. Each of these projects has also reduced (localised) soil loss. However, each of the projects has also helped to enhance the natural ecosystem. In most of the projects, this has been accomplished by plantings and the preservation of ground cover that has helped to maintain the natural hydrological regime. The exception to this generalisation, the control of the vinal that has actually resulting in the reduction of tree cover, has also enhanced the natural environment through the preservation of natural grasslands and their associated habitat. Each of these projects has been accomplished at very low cost (generally less than US $ 10,000 to US $ 15,000 each, although the construction of the nearly 200 erosion control dikes cost about US $ 50,000), and with extensive community involvement and participation. Such local, hands-on involvement bodes well for the sustainability of these projects and their continuity within the target communities.

F. Lessons learned

Each of the foregoing case studies has demonstrated the application of various types of phytotechnologies and the utilisation of ecohydrological principles in mitigating and managing water resources-related environmental problems in various areas of the world and in various climatic regimes. In each case, the key to success has been a combination of local knowledge, community involvement, and the use of financial incentives, sometimes direct in the form of grants and loans and sometimes indirect in the form of other incentives, such as increased income potentials or reduced yard care costs. In addition, each case study has also demonstrated the benefits of the application of human ingenuity working in concert with nature to achieve an end that not only has human economic benefit but which also provides or maintains wildlife habitat and natural ecohydrological cycle that remain in balance with the ability of the environment to support human activities within a variety of catchments. In so doing, the case studies have underlined, too, the utility and efficacy of a catchment-based approach to water resources management. These basic elements will be further explored and discussed in the following chapters, which identify the tools and approaches necessary to develop and implement successful ecohydrological projects.

 

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