Impacts of Furrow Irrigation on Shesher and Welala Natural Reservoirs of Lake Tana Sub Basin, Ethiopia

The survey was conducted from March 2012 to March 2013 based on field observations and samples. Shesher is natural reservoir of Lake Tana found at coordinates of 0350300 and 1322162 UTM and at altitudes 1805 a.s.l. Welala natural reservoir is found at UTM coordinates of 0348348 and 1326081 with altitude of 1804 a.s.l. The area of Shesher and Welala was estimated about 500 ha and 110 ha respectively, which are impounded by open water for extended period of a year and both with maximum depth of 3 m during rainy season. Both reservoirs filled their capacity during the rainy season through the inflow river of Ribb and the surrounding flood plain. But during pick dry season of March, 2012 and March 2013 the survey showed unexpected, amazing and sudden death of a home for many biodiversity that both Shesher and Welala natural reservoirs dried up totally. Birds fetch their food from remnants small shrink wet mud spot and it is not uncommon to see remnant dead fishes eaten by birds. This is due to several and unlimited human encroachments mainly for crop cultivation, with out any rules and regulations. Major crops cultivated by drained two reservoirs using gravitational force were Eragrastis teff, Cheak pea, Grass pea, Lentils and Safflower. During dry season no one could be able found drinking water even for their animals and humans, inhabitants started digging well to fetch water from the middle of Shesher and Welala reservoirs. The drainage system was carried out at every 50 m intervals by making large furrows in both sides of two reservoirs until their water totally vanished. These reservoirs should be properly and sustainably exploited by designing appropriate interventions with out land use change, for instance it could be serve for fisheries, ecotourism and livestock sectors.


Introduction
Direct effects of climate change on wetlands are likely to be accentuating by human induced changes that will increase stress on wetland ecosystems. Up to 60% wetlands have been destroyed in the last 100 years due to drainage, conversion, infrastructure development and pollution. These changes could have been responsible for most of the loss in freshwater biological diversity in the United States in recent decades [1]. Water demand is projected to increase steadily during the coming decades. However, climate change is expected to lead to a decrease in water availability, especially in arid and semi-arid areas. To address this problem, many countries will need to continue efforts to increase reservoir storage capacity to meet the increasing demands for freshwater.
Given the fragility of wetlands, its importance for water supply and the growing pressures to convert them to agriculture uses, there is an urgent need for sustainable use of wetlands. This requires management regimes, which help to maintain some of the natural characteristics of wetlands while also allowing partial conversion to allow activities, which can meet the economic needs of communities. A balance has to be made between the environmental functioning of the two wetlands and their use for livelihood purposes. The purpose of this survey is therefore, to evaluate the current encroachment status of Shesher and Welala natural reservoirs in Lake Tana sub basins. surrounding inhabitants and repeated personal observations were made and coordinates using GPS was taken both during pick rainy seasons and following the decreasing of water volume due to furrow irrigation during pick dry seasons. The possible flooded hectares of the two reservoirs were calculated. Field crops cultivated using water drained from reservoirs by gravitational forces was identified and evaluated.

Shesher natural reservoir
Shesher is natural reservoir of Lake Tana found at coordinates of 0350300 and 1322162 UTM and at altitudes 1805 a.s.l, which filled its capacity during the rainy season through the inflow river of Rib and the surrounding flood plain. This reservoir is estimated with an area of 500 hectares filled with water and free from vegetation cover due to its high relative depth that estimated of maximum depth 3m during the pick rainy season ( Figure 2). According to [4], the surface area of Shesher shirked by 91 % to 136 hectares from what it was 1557 hectares in 1987. The whole boundary of this reservoir was cultivated by the inhabitants with rice production at all water logged areas during the rainy seasons. Most of their livestock are transferred to the neighboring upland community settlements until the harsh flooding condition passed away. Few numbers of cattle mostly oxen and milked cows left to the surrounding fed by collecting weeds from their rice farm. Fishing was the most farming practice during the flooded periods, using predominantly of spears followed by beach seines during post rainy seasons. Clarias gariepinus is the most abundant fish species because its reproductive biology is favored by this natural reservoir of Shesher wetlands.
During pick dry season of March, 2012 the survey showed unexpected, amazing and sudden death of a home for many biodiversity and life full of Shesher natural resource dried up totally and birds fetch their food from remnants small shrieked wet mud spot ( Figure 3). This happened due to several and unlimited human encroachments for different activities mainly for crop cultivation, with out any rules and regulations. Major crops cultivated by drained Sheshers water using gravitational force were Eragrastis teff, Cheak pea, Lentils and Safflower ( Figure 4). It seems the community lacks knowledge and awareness about Shesher reservoir wetland of sustainable use other than exploiting beyond its maximum limit.   During the dry seasons the inhabitants could not be able found drinking water even for their animals and themselves, they started digging well to fetch water from the Shesher reservoir.
Un studied water use that is extensive use of irrigation to all directions of the reservoir causes shortage or even loss of whole available water which leads to wilt and dried of crop prior its ripening periods, there has been a lot of clues such as cracking of soil at early stage of Eragrastis teff and its color also indicates its future negative fate that might end up with non ripe seeds ( Figure 5).
Such type of irrigation system in Shesher reservoir could not be recommended practice because it is not well studied and high pressure was imposed from four kebele inhabitants of its surrounding without calculating its carrying capacity, it drained until the water lost from the area by making furrows even followed its small shrinkage ( Figure   6). Water could not be found even for drinking of their animals and for themselves, as a result they started digging of the ground to fetch water for themselves and their animals (Figure 7).

Welala natural reservoir
Welala wetland is found at UTM coordinates of 0348348 and 1326081 with altitude of 1804 a.s.l. The surface area of Welala is estimated about 110 ha, which is impounded by open water for along period of a year with maximum depth of 3m during rainy season. According to [4], its surface area was 159 hectares shirked by 47 % from what it was 298 ha in 1987. Welala wetland was imposed by one kebele only, Nabega Giorgis that has bylaw, to be assigned only for communal grazing land in contrast to Shesher wetland. But human encroachment is defined here by draining water in both directions for crop cultivation on neighboring lands other than Welala territories. The drainage system carried out at every 50 m intervals by making large furrows in both sides of Welala (Figure 8), as a result the volume decreased very rapidly and becomes unable of supporting the biota of Welala ecosystems.
Especially fishes and birds are seriously affected during the pick dry seasons of the area and it is not uncommon to see remnant dead fishes eaten by birds (Figure 9). If Welala wetland could be protected from several imposed activities from the inhabitants it might be properly exploited by designing appropriate interventions for instance it can serve for fisheries and ecotourism activities ( Figure  10).
Livestock production system in Welala wetland became totally dependent on leftovers and residues of crop production because during the rainy season cattle left the area due to high volume of flooding problem and during the dry seasons the area was shifted to crop cultivated land. The only area considered for communal grazing land by the community was the open water of Welala during its drainage period assuming the area becomes devoid of water. But there has not been observed any foraging types, it was free from vegetation cover and livestock of the surrounding waiting for watering systems   Tewabe (2015) 004 from underground water and feeds from supplements probably of crop residues (Figure 11). The area is known for breeds of Fogera with their high performance traits.
According to the 100 interviewed respondents from Shesher and Welala surrounding villages, replied that 100 % of them were engaged in fishing especially during pick and post rainy seasons of a year. About 95% from Shesher and 75% from Welala responded that they were using the wetlands for cattle grazing through out the year in the previous years. According to the Intergovernmental Panel on Climate Change (IPCC).The new knowledge enables IPCC to improve their   methodological guidance for monitoring greenhouse gas emissions from wetlands significantly. In the current IPCC guidelines (2006), considerable gaps exist with regard to emissions of wetlands, and particularly with respect to rewetting of drained peatlands. Peatlands drained for practices such as agriculture or forestry are significant sources of emissions, which can be reduced by rewetting (increasing the water Table 1) [5]. According to [6] a total of 274 benthic macroinvertebrate individuals belonging to 5 families were collected, 32, 699 individual birds belonging to 62 species were enumerated and 13 species of macrophytes were identified.

Conclusion
The two wetlands were shrinked and finally dried up at an alarming rate starting from November to the end of March, mainly because of unsustainable agricultural farming practices; farming practices by draining water through furrow irrigation system. Fishery recruitment of Lake Tana and other biodiversities like bird population have been adversely impacted by the present irrigation activity. Nowadays lack of communal grazing lands due to the dried up of these two wetlands through excessive furrow irrigation, Fogera cattle breeds are displaced by low performed upland breeds (personal communication and observation). In focus group discussions in both villages, all came to the consensus that all of them benefitted from the wetlands in fishing, cattle grazing and aesthetic values than converted to farm lands for crop production. During the last 20 years, Shesher Wetland shrinked from 1,557 hectares to 500 hectares and Welala shrinked from 298 hectares to 110 hectares. In the present study, during the dry seasons the two wetlands shrieked to 100% (totally dried up). From field observations it was clear that Shesher Wetland dries earlier in the dry season than Welala wetland.  During pick dry season of March 2012 and March 2013 the survey showed unexpected, amazing and sudden death of a home for many biodiversity wetlands, Shesher and Welala natural reservoirs dried up totally. Birds fetch their food from remnants small shrink wet mud spot and it is not uncommon to see remnant dead fishes eaten by birds. This is due to several and unlimited human encroachments mainly for crop cultivation by furrow irrigation system, with out any rules and regulations made by respective actors.

Recommendations
• Environmental friendly developmental activities have to be in place, as a result appropriate and sustainable exploitation of Shesher and Welala reservoirs would be achieved and natural resources of Fogera flood plain sustained.
• An integrated landscape approach to these catchment and wetland rehabilitation is required in order to reverse the trend towards desertification of these wetlands and improve livelihoods and well-being of the community. We suggest that it may still be possible to avoid the most catastrophic impacts of encroachment and land use change.
• Particularly Clarias gariepinus fish stock of lake Tana would be seriously affected by recruitment overfishing, if these two wetlands could not be properly utilized and conserved with out land use change.
• It needs further multidisciplinary investigations and developed management plans