Exploring the village tank cascade systems (VTCSs) in Vavuniya district, Sri Lanka

An attempt was made to identify, validate the village tank cascade systems (VTCSs) and study the water flow from one village tank to another in each VTCS in the eight Agrarian Service Centre (ASC) divisions in the Vavuniya district from October 2017 to December 2018. VTCS contributes a significant share of available water resources for the livelihoods of households in the Vavuniya district. The 1:10,000 topographic map of the Survey Department, satellite images and the digital elevation model were used to identify the cascades and flow direction map for the study area using ArcGIS 10.2.2. Among 756 village tanks in the district, 80 VTCSs comprising 514 village tanks were identified, and only 69 cascades were validated in the field. In addition, this study identified 111 isolated village tanks without connecting with other village tanks and 131 abandoned village tanks. Further investigation is recommended to explore the possibilities of increasing the cascade areas in the study area by connecting isolated tanks with VTCSs. Initiation taken toward rehabilitation of cascades would enhance the livelihood of farm households in the Vavuniya district and lead to sustainable water resource management.

Sustainability of Village Tank Cascade Systems of Sri Lanka: Exploring Cascade Anatomy and Socio-Ecological Nexus for Ecological Restoration Planning

Village Tank Cascade Systems (VTCSs) in the Dry Zone of Sri Lanka have evolved as sustainable ecosystems through human interventions to ensure water availability and other services for people and their environs during the last few millennia. However, VTCSs are vulnerable to global environmental changes resulting in continual deterioration of ecological health and hydro-socio-ecological status, crucial for the food and livelihood security of rural farming communities in the dry zone. This paper seeks to explore resource systems of the Mahakanumulla VTCS located in Anuradhapura district of Sri Lanka to (i) identify the spatial metrics linked to the sustainability and socio-ecological resilience of the VTCS, and (ii) determine interactions among system elements and their impacts on productivity and restoration challenges. The spatial analysis was conducted using a Digital Elevation Model (DEM), recent digital topographic map layers and Google Earth images to understand the spatial distribution and ensemble of tank environs. Participatory field assessment data were also used to determine socio-ecological nexus and factors that contribute to the reduction of ecological productivity of VTCS. The study revealed that the ensemble of tank environs is significant for providing regulatory and supporting ecosystem services (ES) and synergistic relationships with provisional ES of the VTCS. Results also revealed that the complex land-water-biodiversity-climate and food nexus that determines the productivity of the VTCS could be adopted in VTCS ecological restoration planning. The study presents a comprehensive framework to analyse causal factors and processes leading to reduction of overall productivity linked with variables of socio-ecological properties, vulnerability and resilience of the VTCS landscape.

Constructive and technological substantiation of constructive solutions for mountain bridge structures

In this article structural concepts peculiarities of bridge structures for mountain conditions were analyzed. It is noted that the mountainous terrain is characterized not only by a complex broken rock but also by the course of earthquakes and their genetic varieties: landslides, avalanches, rockfalls, etc. It is also noted that the interaction of the plain bridge and the environment is one-sided, while mountainous bridges themselves are negatively influenced by the mountainous environment. The Republic of Dagestan territory is considered an example of mountainous terrain. The linking bridge structures problem to various mountainous terrain regions is investigated here. The peculiarity of the mountain rivers and bridge crossings interaction is noted in this paper, as well as the influence of rivers on the constructive justification of the mountain bridges solutions. The possibility of using cascade systems for regulating the mountain rivers water regime for the rational bridge crossings design with several holes is considered. Various options for the bridge crossings placement relative to mountain rivers are given as well as described their peculiarities. Current support parts and expansion joints are considered and analyzed from the mountain bridge use on structures suitability point of view. The necessity of using seismic-insulating expansion joints and their influence on the conditions of vehicles passing through the bridge structure during an earthquake is substantiated here. The problem of using road pavements on mountain bridge structures is noted, the most common road pavements designs are described and analyzed. The concepts of the «ideal» bridge and their applied significance in relation to mountainous terrain are presented. The constructive and technological solutions considered within the framework of this article will improve the bridge structure’s efficiency in mountainous conditions.