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<Technology Needs for Lake Management in Indonesia - Investigation of Rawa Danau and Rawa Pening, Java> Q. Conclusions on Technological Needs for Rawa Pening (Section 6 to 12) 6. Risks of disease imposed by poor waste management in the catchment Faecal contamination of water used for domestic purposes creates a risk of contraction of a number of bacterial and protozoal diseases. Among these are such well known diseases as typhoid and bacterial dysentery. The relevant technology for the prevention of such diseases has already been mentioned. It amounts to the elimination of water contamination in the catchment. Other diseases stem from polluted water. These include malaria and dengue. The polluted water is an attraction to mosquitos laying eggs as the pollutant, if organic, provides a source of food for mosquito larvae. The vector, a mosquito such as Aedes aegypti, will prosper in any temporary body of water, even in flower pots and discarded tyres. Where polluted water is abundant, the mosquitos are also abundant. To limit the populations of mosquitos it may be desirable to breed and release quantities of small fish such as Galaxiids or some indigenous species which are known to feed on mosquito larvae. This is a better solution than spraying pools of water with insecticide. Sprays are expensive and the application is time consuming, fish are relatively cheap and do the work for you. The losses to malaria, dengue, typhus, and typhoid, are expensive in several ways. They cost human lives in some cases and certainly cause much human suffering. From the economic viewpoint they cause loss of working days, and the community is require to invest in hospitals and doctors. Medicine has to be manufactured or imported at substantial cost. These costs, to the individual and to the community, could be minimised if appropriate measures were taken to reduce water pollution. Poor management of solid waste disposal and collection systems can also cause a range of health problems. The run-off from dumps flowing eventually into rivers causes a similar range of illnesses as described above. These include bacillary dysentery and typhoid. Rats abound in garbage dumps and the rats themselves are hosts of several parasites which transmit disease. These include Leptospirosis (Weil's disease) which is, or can be, carried in water, and infection follows drinking water contaminated with rat urine. This is a serious illness though not usually fatal. The more familiar disease associated with rats is plague where the host is a flea living on the rat. The flea can be passed on to a person and then infects the individual with the bacterium of plague (Pasteurella pestis). In several areas in Indonesia, rats have become notorious for their role in the transmission of typhus. The host is a mite living on the rats, and during land clearing for new developments, rats are disturbed and mites are 'collected' by workers on their clothing. Subsequently the workers contract typhus which can prevent them doing any labour for up to six weeks. As a separate issue rats are known to cause the loss of up to 30% of the total crop of rice in some areas of Indonesia. To have breeding grounds for rats in solid waste disposal sites in the catchments is to subsidise the loss of food to rats. A casual walk along the banks of any of the rivers entering Rawa Pening reveals rat burrows. Rat catching campaigns are held periodically in the area. These are pointless as the capacity of the rats to breed means that within about 4 months the rat population is probably the same size as before the rat catching campaign. The quality of life of many of the rice farmers in the area would be improved if they could add another 30% in area to the fields they cultivate. As an alternative, they would gain the same amount of increased revenue if they could eliminate or reduce substantially the numbers of rats in the area. It has been pointed out in Kalimantan that rats in transmigration areas could be controlled by the introduction of nesting boxes for barn owls, which are native to Indonesia. These large owls feed selectively on rats. There would seem to be no reason why nesting boxes suitable for barn owls should not be introduced to the forest areas on the shores of the lake. The owls forage for preference in fields and would utilise the open field of the edge of the lake as a feeding ground. In general the control of rat populations is a never ending battle. But much can be achieved by good management of solid waste disposal facilities and by the introduction of barn owls to suitable habitats. If the owls are introduced, then the public must be informed that they are valuable birds. All too often one sees every weekend in Java, youths carrying rifles or shotguns looking for a bird or mammal to shoot. Few large birds survive outside nature reserves and even there they are not safe from the hunter. Traps can be set on dykes in the lake and on the banks of rivers leading into the lake. The entrances to burrows should be blocked whenever possible. This would probably be as effective as having days spent on rat catching campaigns. It is important to be able to make some predictions of the potential risks to the environment and to people and of the consequences in the future of their exposure to environmental hazards. This can be carried out using Environmental Risk Assessment - a soft technology. IETC has published a Technical Report (No. 3), Environmental Risk Assessment for Sustainable Cities. This Manual contains much material which could be relevant to the management of risks such as those mentioned above in urban and peri-urban areas in the catchment. 7. Soil erosion in the catchment, its consequences and control It has been recognised for a long time that soil erosion affects water quality by adding quantities of clay, organic matter and dissolved chemicals such as plant nutrients to surface water flows. This process also leads to the loss of soil stability, fertility and therefore productivity. For many years agricultural technology has been concerned with methods of limitation of soil loss. It is to books on agricultural technology that one should turn for information on technologies to limit this process. In tropical Java certain technologies are well known and effective. When land is cleared for development of any kind, cover crops should be planted at once. These include a range of rapidly growing leguminous herbs, which reduce the effects of rainfall on bare earth, add nitrogenous compounds to disturbed soil, and provide a fast growing crop for local farmers. Such leguminous cover crops should become a compulsory part of any development scheme as they do not interfere with the construction process to any significant extent. In the Rawa Pening catchment they should have been planted on exposed land cleared for house construction, and for hotels. Contour ploughing and contour cultivation lead to the development of terraces. These can be seen throughout the catchment. In some cases, the run-off from the terraces is directed towards gutters at the roadside, which is not the best end point for rainwater carrying sediment and plant nutrients which are valuable to the farmer. A further step for the farmer towards control of nutrient and soil loss is the development, particularly on steep unstable soils, of agro-forestry. In this agro-ecological system, trees which contribute to the agro-economic system are planted in rows, usually along the edge of contour terraces, to provide reinforcement and support for the terrace, as well as shade and shelter for crop plants planted on the terraces. Suitable trees for an agro-ecological system would include such species as Leucaena, which provides shade for crops, fodder for stock, and, since it is leguminous, nitrogen for the soil. The wood is useful for burning, for heating and cooking. Rows of trees such as Leucaena are commonly seen in Java along with fruit trees, such as durian, jackfruit, and mango trees. These trees provide valuable income to the farmer. Hill areas in the catchment which have become de-forested either through illegal felling of trees or as a result of volcanic action, should be re-forested. The Government has a very comprehensive re-greening program which is carried out by the Directorate of Reboisasi (Re-forestation) in the Department of Forestry. Regrettably the sums made available to this organisation never seem to be sufficient to allow it to catch up with the backlog of work waiting to be undertaken. Re-forestation is an on-going process. Tree species and crops suitable for cultivation in agro-forestry at one altitude in this catchment may not be at all suitable at another altitude, since the altitudinal range is over 2,500 metres. Throughout discussions of control of soil erosion, there is a tendency to overlook the point that at present, water is one of the commodities which is most valuable to the farmer. This has to be the focus of the present investigation. The development of rational planning for appropriate developments in a catchment, and particularly in a catchment with soils as fragile as in this case, should depend on the production of maps of land forms, soil type, land capability, existing land use, and land use planning among others. No maps dealing with these aspects of catchment management and decision making appeared to be available to the investigators. Maps of this kind should be available in BAPPEDA, the Provincial Planning Office. It would seem to be essential, as a prerequisite to any form of rational development in this catchment, to produce such maps. The production of such maps should be a prerequisite of the AMDAL (Environmental Impact Assessment) procedures for assessment of major developments in the catchment, such as the development of new major roads and major facilities such as the bus station at Bawen. The input of sediment to the lake is itself a problem at present and is likely to remain so for a number of years even if the Government implements immediately a policy to control soil erosion in the catchment. The input of sediment may be reduced by the construction of checkdams on some of the incoming rivers with high sediment loads. There are no good data available in Java at present on the cost-benefit analysis of the construction of checkdams. One problem is that checkdams are not a once-off piece of construction work. Once constructed they fill up and after an appropriate period have to be emptied or they lose all functional value. There appears to be some doubt in the minds of water engineers in Java at present as to whether it is cheaper simply to build another dam rather than to clean out an existing dam. In the case of Rawa Pening, the amount of land available for the construction of checkdams is severely limited by the local topography in the case of many of the rivers and so the development of a multiplicity of small dams is not likely in this case. 8. Soil accumulation in Rawa Pening The input of soil at the present time to Rawa Pening is not quantifiable. There appear to be no available data. There is an output of soil from Rawa Pening in two directions. The first is the movement of soil in suspension downriver through the overflow from the dam on the Tuntang river, and by flow through the turbines at Jeklok coming from the same dam. From the point of view of the volume of soil lost in this way compared with the volume coming into the lake, the amount lost is probably insignificant. The second is the removal of soil for fertiliser by a number of small industries around the lake. The soil removed is largely organic matter from the sub-fossil remains of the swamp forest which covered the area before the dam was created. Thus although appreciable quantities of soil are removed these are not the incoming gravels, sands and clays eroded from the catchment. The quantity of incoming matter is probably much larger than the volume of organic matter removed each year. 9. Quality of water entering Rawa Pening River water enters Rawa Pening carrying plant nutrients, bacteria, silt, clay and toxic chemicals from diverse sources in the catchments. There is no effective way to treat this incoming river water at the point where it enters the lake, in order to improve water quality in the lake as a whole. While water treatment systems are well known, these are used on relatively small volumes of water at water treatment plants prior to distribution to households in a water supply reticulation system. In this case the initial quality of the water entering Rawa Pening is dependent on environmental conditions in the catchment. It is possible to remove phosphates and some nitrogenous compounds from large volumes of water by allowing the water to flow through swamps (USEPA, 1986). Such swamps can be constructed in appropriate localities using earth moving equipment and concrete. A number of genera of water plants have been used as "sponges" to mop up plant nutrients. One of the most effective is Typha the bullrush or reed mace (Weir, 1976, 1979). Some of the genera of macrophytes have been used a sponges to mop up heavy metals. In the case of Rawa Pening, there is no evidence of heavy metal pollution, since the investigating team are not aware of any analyses for heavy metals undertaken in the last 10 years. If this environmentally sound technology were to be used at Rawa Pening, it would call for the use of large areas of littoral flats for development as artificial swamps. This would disadvantage many of the local villagers who cultivate the flats. The flats are very productive and normally produce two crops of rice per annum. The development of beds of macrophytes as sponges to remove phosphates and similar plant nutrients depends on the capacity to harvest the macrophytes efficiently at intervals, while they are growing. Since Typha has a large rhizome, it grows throughout the year if the ambient temperature is suitable and if water is available. Under these conditions Typha can be harvested periodically throughout the year without materially affecting the production of new foliage from the rhizome. Typha is known to occur in Rawa Pening, but would have to be selectively cultivated for this purpose. Therefore, it appears that the quality of the water entering the lake could be improved for the benefit of local residents, but only at the cost of some sacrifice of the land on which the local residents are dependent for this survival. If the use of artificial swamps as described above, involved an excessive demand for land area to construct the swamp on the available area of the lake flats, then the use of surface flow of water as a type of water treatment would be even less satisfactory. This is used as a form of water treatment in areas where land is available cheaply and is usually followed by some form of ground infiltration. At Rawa Pening ground infiltration is not recommended, as the height differentials, particularly in the wet season, are not adequate to ensure adequate treatment in the heavy clay soils of the littoral flats. 10. Quality of water in Rawa Pening No contemporary data appeared to be available on water quality and water chemistry in Rawa Pening. Data from the period before 1979 showed that, even at that time, the levels of phosphorus were high. It would be a reasonable assumption that environmental processes in the catchment continue, at the present day, to maintain high levels of phosphates and nitrogenous compounds in water in the rivers entering Rawa Pening. If there is any desire to improve water quality in Rawa Pening the most obvious forms of improvement would be to reduce the levels of phosphates and other plant nutrients in the lake water, as well as the levels of bacteria. There are few economic methods for the treatment of water in a lake by removal of phosphates and nitrogenous compounds once they have entered the lake. The two methods which have been considered as being environmentally sound are by the use of macrophytes and by aeration of the lake water. In the case of Rawa Pening both methods are feasible. The use of macrophytes such as Typha to remove phosphates from water has been described above. Eichornia crassipes has also been used for this purpose. In terms of phosphate uptake per square metre per annum it is less efficient than Typha. But since Eichornia already exists in large quantities on the lake it is necessary to examine the possibility of its use in water treatment. The abundance of the macrophyte Eichornia crassipes on Rawa Pening suggests that it could be used as a source of phosphates and nitrogenous compounds on fields used for growing crops. In fact it could be used as green fertiliser and this is actually done in some areas near the lake. The trouble with the use of Eichornia as a green fertiliser is that it is expensive to transport any distance from the lake shore. In the absence of a permanent rooted rhizome like Typha it cannot be used a perennial crop, but has to be cropped by removal of the entire plant at regular intervals. Therefore if Eichornia is to be used as a "cleaning agent" for the water in the lake, it will only be possible if an economically viable use is found for large quantities of Eichornia. There has been no comprehensive investigation of the value of Eichornia in the lake from this viewpoint. The uses which have been found for Eichornia are detailed elsewhere in this report. The difficulties which have been encountered in development of any industry based on the use of Eichornia are also detailed. There are several reports on the economic value of wetlands but none reveal any assessment of a problem such as this with Eichornia. Most of these reports deal with the issue of coastal marshes though the paper by Gupta and Foster (1975), assesses the economic criteria involved in management of freshwater marshes in the Eastern USA. A recent publication by UNEP and Wetlands International (1997) entitled "Wetlands and Integrated River Basin Management" provides information on the functions and benefits of wetlands, amongst other relevant topics. The difficulties with the actual use of Eichornia can be summarised under two headings - first the large clumps of floating plants are difficult to pull out of the water, and second the plants are heavy and expensive to transport any distance from the lake. This contrasts with Typha where the foliage can be cut mechanically and the heavy rhizome left to produce another crop. The second approach is based on aeration of the lake. This technology is used in cases where a lake is stratified and the water in the lower layers of the hypolimnion are de-oxygenated. Under those circumstances phosphates are released from the de-oxygenated sediments of the lake bottom, into the hypolimnion. Aeration then causes the phosphates to become re-adsorbed on the clays on the bottom sediments. This is not the case in Rawa Pening. As has been mentioned previously, there is no evidence of de-oxygenation in Rawa Pening. Thus the effects of aeration would have to be investigated to determine whether the process produced any significant reduction in phosphate levels in the lake. In other respects, aeration might increase the population of fish or the size of fish produced by the lake, by altering the areas of water accessible to particular species of fish. Aeration could be carried out in a variety of ways, either from floating platforms or from fixed jets set on the bottom of the lake and sending a spray of water into the air. Of these the bubbling of air through the water is cheaper in terms of fuel usage and of capital equipment. Many different pumps and spray heads have been used for this purpose. It has been shown that simple curtain of bubbles is very effective in aeration and in destruction of a hypolimnion. 11. Environmental impact of introduced technologies If technologies such as those discussed above were to be implemented on this lake, the impacts of the technology on the environment would have to be assessed. It would be necessary to define in advance of introducing the technology, exactly what effects the technology is expected to achieve. It would then be possible to assess after a sufficient period of time had passed whether the technology had achieved the desired effect. The methodology for such assessments is well known and involves the use of the AMDAL or Environmental Impact Assessment procedure. One major problem may be the availability of technical expertise to assess the effects of the technologies, or to obtain the technical data which will provide a basis for decision making. Universitas Kristen Satya Wacana has an established record of involvement with all aspects of the environmental system of the lake and its catchment. It would be appropriate to reconstitute the Limnological Research and Teaching Laboratory formerly maintained by this University at Rawa Pening. Such a laboratory could be used as the field centre for scientific investigations of Rawa Pening. Student involvement would provide a basis for the accumulation of data covering many aspects of the ecology of the lake and its environment. In this connection, the Technical Publication by IETC (1997B), Training Needs in Utilising Environmental Technology Assessment (EnTA) for Decision-Making, would be relevant as would the Workbook for Training in Adopting, Applying and Operating Environmentally Sound Technologies (ESTs) (IETC, 1997A). Working materials for a workshop on the latter subject focused on Urban Management are available and would also be relevant in selecting technologies which would be suitable for use in the management of Rawa Pening and the surrounding area with its human settlements. 12. Technological viewpoints on other possible developments There have been suggestions that Rawa Pening will be developed as part of the large Jratunseluna Project. This apparently involves the creation of a dam wall round much of the lake to increase the depth of the lake and effectively double its holding capacity. It is felt that much of the water passing through Rawa Pening should be held in the lake and retained for use during the dry season, to provide water for irrigation systems downstream. Presumably any such large Government funded development would be subject to an AMDAL assessment, which would be evaluated by an impersonal authority. Certain changes in the ecological systems of the lake might be predictable, if this Project were to be implemented. The maintenance of a constant water level, wet season and dry season, would provide an opportunity for the water hyacinth to spread over the surface of the lake. Normally a large number of plants are killed annually by desiccation on the lake flats as the water level falls. Others are killed by incorporation into the walls of temporary padi fields constructed on the exposed mud flats as the water level falls. If water hyacinth plants were to spread over the surface of the lake, the possibility of de-oxygenation would increase rapidly. The fishing industry would cease to exist, recreational fishing and sailing on the lake would stop. The extraction of soil from the bed of the lake for fertiliser would become very difficult, both because of the increased depth of water during the dry season and because of the difficulty of getting through the beds of water hyacinth with heavily loaded boats. The probability is that Government would attempt to control the water plants by the use of chemical herbicides. These have been shown to be relatively effective but to produce unfortunate side effects on the environment. If large quantities of water hyacinth are killed in a small body of water, large quantities of plant nutrients such as phosphates are released into the water. In many cases these have caused algal blooms, where, often, the bloom is of toxic blue-green bacteria, which are not affected by herbicides. The suggestion of creating a wall round the lake to deepen it has implications for the small villages on the shore of the lake. Many of these would be adversely affected, the villages in some cases being under water. The agricultural land of the littoral flats would be lost for rice production. There is little indication of how a water release scheme for rice growers on the shore would fare, and in particular of how water could be distributed to the rice growers, if the level of the lake were raised. New flood control measures would be necessary and a substantial part of the town of Ambarawa would either be under water after the creation of the new lake or would be below the new level of the lake and protected by an earth wall. Exactly how some of the present rivers could flow into the lake is unclear. If Rawa Pening were to become the centre of a new tourist industry, then it would be necessary to improve the water quality in the lake as well as the fishing potential of the lake. It would be necessary to develop an effective system of sewage reticulation and disposal for the restaurants and hotels being developed on the shore of the lake. It is likely that there would be increased pressure for the development of recreational sailing and fishing on the lake. All this would be, to varied extents, incompatible with the creation of an embankment to deepen the lake. Tourism would bring pressures for the reduction of biting insects such as mosquitos and rats, so would require the improvement in the solid waste collection and disposal system.
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