Abstract
People in the dry zone of Sri Lanka where hydraulic civilization once thrived, suffer from occurrence of a chronic kidney disease of unknown etiology (CKDu). The etiology for CKDu is now shown to be multi factorials and but related to water. Ancient people in the dry zone used surface water of tank cascades system and this system was interlinked with the ecosystem and social system of the area. It is hypothesized that the adverse changes that took place to the ecosystem of the tank cascade system and new commercial practices of agriculture in the CKDu prevalent area have also become reasons for the spreading of CKDu. This review assesses the effect of different components of the tank cascade systems in improving the water quality. A number of studies have reported positive effects of improving the surface water quality of the tank by the Wew Ismaththa (closer catchment), Thaulla (upper peripheral gentle sloping land), Kattakaduwa (Interceptor) Iswetiya or Potawetiya (upstream soil ridges), Godawala (small silt trapping pond). The review also identified functions of Thaulla area approximately similar to a constructed wetland. This review highlights the issues and gaps in our understanding the ecological functioning of Globally Important Agricultural Heritage System. It is suggested that reconstruction of ecofriendly structural components of tanks and reestablishment of tank cascade system in the area would help to combat the spreading of CKDu in dry and intermediate zone of the country.
Highlights
History of Sri Lanka is directly associated with the hydraulic civilization
There is a growing concern over the high incidence of chronic kidney disease of unknown etiology (CKDu) in dry and intermediate zone of Sri Lanka, and the ancient tank cascade system with its ecological functions has a potential for controlling this disease
Various studies exploring the etiology of CKDu suggested that heavy metals cadmium (Bandara et al, 2010; Jayathilake et al, 2013), arsenic (Jayasumana et al, 2013), elevated levels of fluoride in groundwater, the specific composition of groundwater (Chandrajith et al, 2011), aluminum (Illeperuma et al, 2009), weedicide (Jayasumana et al, 2014) and cyanobacterial toxins ( Dissanayake et al, 2011) excessive ground water iconicity ( Dharmawardena et al, 2015), excessive PO4 ions present in water (Dharma-wardana,2017) etc. as causative agents
Summary
History of Sri Lanka is directly associated with the hydraulic civilization. Many civilizations such as Indus, Mexican, Maya and Inca had a long history and flourished with power and knowledge and faded away with passing the time. At present, an appreciable percentage of people in dry zone of Sri Lanka earlier Rajarata and Ruhunu rata where hydraulic civilization thrived suffer from the occurrence of chronic kidney disease of unknown etiology (CKDu). We observed that many hypotheses have been proposed as causative factors for CKDu and established at present as a multifactorial origin. These associated factors are related to water. We believe that this occurrence is due to the drastic changes happened to the hydraulic system of the dry and intermediate zone of the country.
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