Your search found 15 records
1 Singh, R. B.; Mishra, P. 2004. Remote sensing based land use and cover change monitoring as an ecohydrological indicator of sustainability in the Himalayan ungauged basin. In Herath, S.; Pathirana, A.; Weerakoon, S. B. (Eds.). Proceedings of the International Conference on Sustainable Water Resources Management in the Changing Environment of the Monsoon Region. Bandaranaika Memorial International Conference Hall, Colombo, Sri Lanka, 17-19 November 2004. Vol.1. Colombo, Sri Lanka: National Water Resources Secretariat. pp.425-431.
Land use ; Remote sensing ; Forest cover ; Satellite surveys ; Monitoring ; Population growth ; Hydrology ; Ecology ; Land degradation / India / Himalaya / Shimla District
(Location: IWMI-HQ Call no: 333.91 G000 HER Record No: H039527)
2 Ryszkowski, L.; Kedziora, A. 2008. The influence of plant cover structures on water fluxes in agricultural landscapes. In Bossio, Deborah; Geheb, Kim (Eds.). Conserving land, protecting water. Wallingford, UK: CABI; Colombo, Sri Lanka: International Water Management Institute (IWMI); Colombo, Sri Lanka: CGIAR Challenge Program on Water & Food. pp.163-177. (Comprehensive Assessment of Water Management in Agriculture Series 6)
Water shortage ; Ecosystems ; Plant cover ; Forest cover ; Precipitation ; Runoff ; Water management / Poland / Finland / Costa Rica
(Location: IWMI HQ Call no: IWMI 631.7 G000 BOS Record No: H041600)
3 Malmer, A. 2009. Forests working as rainwater harvesting systems. In Barron, J. (Ed.). Rainwater harvesting: a lifeline for human well-being. Nairobi, Kenya: UNEP Division of Environmental Policy Implementation; Stockholm, Sweden: Stockholm Environment Institute. pp.34-43.
Forests ; Forest cover ; Forest ecology ; Water use ; Water harvesting ; Rainwater ; Infiltration ; Water balance / Africa / Southern Africa / Miombo woodland
(Location: IWMI HQ Call no: e-copy only Record No: H042286)
http://www.unep.org/Themes/Freshwater/PDF/Rainwater_Harvesting_090310b.pdf
https://vlibrary.iwmi.org/pdf/H042286.pdf
https://vlibrary.iwmi.org/pdf/H042286.pdf
(0.45 MB)
4 Clement, Floriane; Orange, Didier; Williams, M.; Mulley, C.; Epprecht, M. 2009. Drivers of afforestation in northern Vietnam: assessing local variations using geographically weighted regression. Applied Geography, 29:561-576. [doi: https://doi.org/10.1016/j.apgeog.2009.01.003]
Afforestation ; Forest cover ; Assessment ; Remote sensing ; Regression analysis ; Models ; Forest policy ; Land use ; Households / Vietnam / Hoa Binh Province
(Location: IWMI HQ Call no: e-copy only Record No: H042315)
(0.86 MB)
This article identifies drivers of forest transition in a province of Northern Vietnam between 1993 and 2000 by applying geographically weighted regression (GWR) analysis to remotely sensed and statistical data. The regression model highlighted the spatial variation of the relationship between the percentage of land afforested and its proximate causes. Factors identified as having a major impact on afforestation are: the presence or proximity of a wood-processing industry, the distance to highways, and land allocation to households. Whereas the two former variables are in most areas of the province positively correlated with afforestation, an unexpected negative correlation was observed for the latter. The analysis of these results, supported by an in-depth knowledge of the area and of the political context, leads to the conclusion that, during the time period considered, afforestation was largely driven by state organisations on protected state-owned land, and forestry was not a significant component of household economic activities.
5 Gunatilleke, N.; Jayasuriya, M.; Weerakoon, D.; Gunatilleke, S.; Ranwala, S.; Perera, D.; Wattavidanege, J.; Manamendraarachchi, K.; De Silva, M. A. T.; Wijesinghe, L. 2014. Sri Lanka's forests: nature at your service. Commemorating the decade of biodiversity. Colombo, Sri Lanka: Sri Lanka Association for the Advancement of Science (SLAAS). 155p.
Natural resources ; Forest resources ; Forest cover ; Forest ecology ; Forest degradation ; Forest conservation ; Plants ; Species ; Deforestation ; Vegetation ; Wild animals ; Biodiversity ; Environmental effects ; Human behaviour ; Archaeology ; Water resources ; Catchment areas ; Soil conservation / Sri Lanka / Sinharaja / Kanneliya
(Location: IWMI HQ Call no: 333.75 G744 GUN Record No: H046774)
(0.49 MB)
6 Lacombe, Guillaume; McCartney, Matthew. 2016. Evaluating the flow regulating effects of ecosystems in the Mekong and Volta river basins. Colombo, Sri Lanka: International Water Management Institute (IWMI). 40p. (IWMI Research Report 166) [doi: https://doi.org/10.5337/2016.202]
Ecosystems ; Flow discharge ; Rain ; Temperature ; Floodplains ; Geomorphology ; Geography ; Models ; Land cover ; Land use ; Forest cover ; Water resources ; Soils ; Wetlands ; River basins ; Stream flow ; Downstream control ; Catchment areas ; Paddy fields ; Policy making ; Planning ; Impact assessment ; Living standards ; Runoff / Southeast Asia / China / Burma / Lao People's Democratic Republic / Thailand / Cambodia / Vietnam / Ghana / Burkina Faso / Mekong River Basin / Volta River Basin
(Location: IWMI HQ Call no: IWMI Record No: H047530)
(1 MB)
By altering evapotranspiration and influencing how water is routed and stored in a basin, natural and agrarian ecosystems affect river flow. To quantify the impact of ecosystems on streamflow in two large river basins in Asia and Africa, simple statistical relationships were calculated, enabling flow characteristics to be ascertained from basic catchment features. This approach allows the impact of specified land-use change on streamflow to be determined. For example, it shows that extending paddy areas in the Mekong River Basin reduces downstream low flows, while conversion of forests to crops increases the magnitude of downstream floods in the Volta River Basin. The approach could assist river basin planners to better account for flow-related ecosystem services.
7 Fernando, S. (Ed.); Nadaraja, L. (Photographer). 2016. Sri Lanka: a heritage of water. [s.l.]: Author. 227p.
Water resources ; Watersheds ; Water quality ; Water use ; Hydraulic structures ; Cultural development ; Heritability ; History ; Ancestral technology ; Building construction ; Social groups ; Religion ; Women's participation ; Administrative areas ; Government policy ; Climate change ; River basins ; Seas ; Islands ; Nature reserves ; Forest cover ; Land use ; Lagoons ; Aquatic mammals ; Otters ; Crocodiles ; Waterfowl ; Habitats ; Biodiversity ; Aquatic plants / Jaffna / Kanneliya / Dediyagala / Nakiadeniya / Mahaweli River / Upper Mahaweli Catchment
(Location: IWMI HQ Call no: 333.91 G744 FER Record No: H047921)
(1.07 MB)
8 Lyon, S. W.; King, K.; Polpanich, O.; Lacombe, Guillaume. 2017. Assessing hydrologic changes across the Lower Mekong Basin. Journal of Hydrology: Regional Studies, 12:303-314. [doi: https://doi.org/10.1016/j.ejrh.2017.06.007]
Hydrological factors ; Catchment areas ; River basins ; Models ; Natural resources ; Forest cover ; Deforestation ; Rainfall-runoff relationships ; Wet season ; Dry season ; Evapotranspiration ; Rice ; Land cover ; Stream flow ; Precipitation / Southeast Asia / Lao People's Democratic Republic / Thailand / Cambodia / Vietnam / Lower Mekong Basin
(Location: IWMI HQ Call no: e-copy only Record No: H048179)
http://ac.els-cdn.com/S2214581816302348/1-s2.0-S2214581816302348-main.pdf?_tid=fbab4f94-9de3-11e7-b294-00000aacb362&acdnat=1505898996_0cb0f1fe6d4c4991593d85d0efcf7e92
https://vlibrary.iwmi.org/pdf/H048179.pdf
https://vlibrary.iwmi.org/pdf/H048179.pdf
(906 KB)
Study region : In this study, 33 catchments across the Lower Mekong Basin in Southeast Asia are examined to detect historical changes in their hydrological response via a model-based methodology.
Study focus : Intensive development over the past half century across Southeast Asia’s Lower Mekong Basin has inevitably affected natural resources. Large areas have been converted from forests for subsistence and commercial agriculture, and urban development. We implement an innovative approach to screen hydrologic data for detecting impacts of such large-scale changes on hydrological response. In a first step, temporal changes in the rainfall-runoff relationship were assessed using the parsimonious, two-parameter GR2M hydrological model. In a second step, a distribution-free statistical test was applied to detect whether significant changes have occurred in the wet season (high flow) and dry season (low flow) conditions.
New hydrological insights for the region : Our results indicate that the majority of catchments (64% of those considered) with sufficiently long data records exhibited no discernable trends in hydrological response. Those catchments that did exhibit significant trends in hydrological response were fairly evenly split between increasing trends (between 21% and 24%) and decreasing trends (between 15% and 12%) with time. There was a lack of evidence that these changes where brought about by shifts in precipitation or potential evapotranspiration; however, catchments exhibiting significant increasing trends in hydrological behavior were found to have different land cover compositions (lower percentage of forest coverage and subsequently higher paddy rice coverage) than those exhibiting significant decreasing trends. The approach presented here provides a potentially valuable screening method to highlight regions for further investigation of improved mechanistic understanding. Without this connection, we might be blind to future hydrological shifts that can have significant impact on development.
Study focus : Intensive development over the past half century across Southeast Asia’s Lower Mekong Basin has inevitably affected natural resources. Large areas have been converted from forests for subsistence and commercial agriculture, and urban development. We implement an innovative approach to screen hydrologic data for detecting impacts of such large-scale changes on hydrological response. In a first step, temporal changes in the rainfall-runoff relationship were assessed using the parsimonious, two-parameter GR2M hydrological model. In a second step, a distribution-free statistical test was applied to detect whether significant changes have occurred in the wet season (high flow) and dry season (low flow) conditions.
New hydrological insights for the region : Our results indicate that the majority of catchments (64% of those considered) with sufficiently long data records exhibited no discernable trends in hydrological response. Those catchments that did exhibit significant trends in hydrological response were fairly evenly split between increasing trends (between 21% and 24%) and decreasing trends (between 15% and 12%) with time. There was a lack of evidence that these changes where brought about by shifts in precipitation or potential evapotranspiration; however, catchments exhibiting significant increasing trends in hydrological behavior were found to have different land cover compositions (lower percentage of forest coverage and subsequently higher paddy rice coverage) than those exhibiting significant decreasing trends. The approach presented here provides a potentially valuable screening method to highlight regions for further investigation of improved mechanistic understanding. Without this connection, we might be blind to future hydrological shifts that can have significant impact on development.
9 Guzha, A. C.; Rufino, M. C.; Okoth, S.; Jacobs, S.; Nobrega, R. L. B. 2018. Impacts of land use and land cover change on surface runoff, discharge and low flows: evidence from East Africa. Journal of Hydrology: Regional Studies, 15:49-67. [doi: https://doi.org/10.1016/j.ejrh.2017.11.005]
Land use ; Land cover change ; Surface runoff ; Water resources ; Rivers ; Flow discharge ; Catchment areas ; Forest cover ; Soils ; Rain ; Hydrological factors ; Models ; Case studies / East Africa / Kenya / Ethiopia / Tanzania
(Location: IWMI HQ Call no: e-copy only Record No: H048527)
https://www.sciencedirect.com/science/article/pii/S2214581817302161/pdfft?md5=365b6a81188e75ed8aaa40d4564d9fe4&pid=1-s2.0-S2214581817302161-main.pdf
https://vlibrary.iwmi.org/pdf/H048527.pdf
https://vlibrary.iwmi.org/pdf/H048527.pdf
(1.08 MB) (1.08 MB)
Region: East Africa.
Focus: A review of catchment studies (n = 37) conducted in East Africa evaluating the impacts of Land Use and Land Cover Changes (LULCC) on discharge, surface runoff, and low flows.
New hydrological insights: Forest cover loss is accompanied by increased stream discharges and surface runoff. No significant difference in stream discharge is observed between bamboo and pine plantation catchments, and between cultivated and tea plantation catchments. Trend analyses show that despite forest cover loss, 63% of the watersheds show non-significant changes in annual discharges while 31% show increasing trends. Half of the watersheds show non-significant trends in wet season flows and low flows while 35% reveal decreasing trends in low flows. Modeling studies estimate that forest cover loss increases annual discharges and surface runoff by 16 ± 5.5% and 45 ± 14%, respectively. Peak flows increased by a mean of 10 ± 2.8% while low flows decreased by a mean of 7 ± 5.3%. Increased forest cover decreases annual discharges and surface runoff by 13 ± 1.9% and 25 ± 5%, respectively. Weak correlations between forest cover and runoff (r = 0.42, p < 0.05), mean discharge (r = 0.63, p < 0.05) and peak discharge (r = 0.67, p < 0.05) indicate that forest cover alone is not an accurate predictor of hydrological fluxes in East African catchments. The variability in these results supports the need for long-term field monitoring to better understand catchment responses and to improve the calibration of currently used simulation models.
Focus: A review of catchment studies (n = 37) conducted in East Africa evaluating the impacts of Land Use and Land Cover Changes (LULCC) on discharge, surface runoff, and low flows.
New hydrological insights: Forest cover loss is accompanied by increased stream discharges and surface runoff. No significant difference in stream discharge is observed between bamboo and pine plantation catchments, and between cultivated and tea plantation catchments. Trend analyses show that despite forest cover loss, 63% of the watersheds show non-significant changes in annual discharges while 31% show increasing trends. Half of the watersheds show non-significant trends in wet season flows and low flows while 35% reveal decreasing trends in low flows. Modeling studies estimate that forest cover loss increases annual discharges and surface runoff by 16 ± 5.5% and 45 ± 14%, respectively. Peak flows increased by a mean of 10 ± 2.8% while low flows decreased by a mean of 7 ± 5.3%. Increased forest cover decreases annual discharges and surface runoff by 13 ± 1.9% and 25 ± 5%, respectively. Weak correlations between forest cover and runoff (r = 0.42, p < 0.05), mean discharge (r = 0.63, p < 0.05) and peak discharge (r = 0.67, p < 0.05) indicate that forest cover alone is not an accurate predictor of hydrological fluxes in East African catchments. The variability in these results supports the need for long-term field monitoring to better understand catchment responses and to improve the calibration of currently used simulation models.
10 Zhang, K.; Sun, X.; Jin, Y.; Liu, J.; Wang, R.; Zhang, S. 2020. Development models matter to the mutual growth of ecosystem services and household incomes in developing rural neighborhoods. Ecological Indicators, 115:106363. (Online first) [doi: https://doi.org/10.1016/j.ecolind.2020.106363]
Ecosystem services ; Household income ; Rural development ; Urbanization ; Sustainable development ; Forest cover ; Land use ; Indicators ; Policies ; Villages / China / Shandong
(Location: IWMI HQ Call no: e-copy only Record No: H049707)
(1.48 MB)
In the context of rapid urbanization, many rural communities are experiencing dramatic increases in the proportion of construction land, leading to the diminishment of ecosystem services. Conflicting development goals are a primary challenge to sustainable rural development. Increasing household income is a primary rural development concern and harmonizing the relationship between sustaining ecosystem services and increasing household incomes is critical for rural communities. To understand the factors which influence ecosystem services, household income and their mutual growth, an assessment of ecosystem services bound to land-use was carried out in 30 villages in the rapidly developing Shandong Province in eastern China. In this survey the impacts of different land use and development models on the mutual growth of ecosystem services and rural household incomes was analyzed. The results show significant variation in both ecosystem services and household incomes resulting from the implementation of four different development models. The sole ecotourism village in the survey was found to have the highest ecosystem services and household incomes, while ecological protection villages had higher ecosystem services but lower household incomes. Development models may influence ecosystem services by changing land use, and forest cover was the most important influencing factor. It was found that the Type A model, consisting of high forest cover and high marketization of ecosystem services, promoted the mutual growth of ecosystem services and household incomes. These findings suggest that appropriate development models can lead to the harmonious mutual growth of ecosystem services and rural household incomes. We argue that the methods used in this study can help improve rural management in China and elsewhere.
11 Zaveri, E.; Russ, J.; Damania, R. 2020. Rainfall anomalies are a significant driver of cropland expansion. Proceedings of the National Academy of Sciences of the United States of America, 117(19):10225-10233. [doi: https://doi.org/10.1073/pnas.1910719117]
Farmland ; Rain ; Agricultural productivity ; Land use change ; Deforestation ; Dams ; Policies ; Climate change ; Smallholders ; Farmers ; Irrigation ; Infrastructure ; Forest cover ; Precipitation ; Developing countries
(Location: IWMI HQ Call no: e-copy only Record No: H049998)
(0.67 MB) (684 KB)
Rainfall anomalies have long occupied center stage in policy discussions, and understanding their impacts on agricultural production has become more important as climate change intensifies. However, the global scale of rainfall-induced productivity shocks on changes in cropland is yet to be quantified. Here we identify how rainfall anomalies impact observed patterns of cropped areas at a global scale by leveraging locally determined unexpected variations in rainfall. Employing disaggregated panel data at the grid level, we find that repeated dry anomalies lead to an increase in cropland expansion in developing countries. No discernible effects are detected from repeated wet events. That these effects are confined to developing countries, which are often dominated by small-holder farmers, implies that they may be in response to reduced yields. The estimates suggest that overall, in developing countries, dry anomalies account for ~9% of the rate of cropland expansion over the past two decades. We perform several tests to check for consistency and robustness of this relationship. First, using forest cover as an alternative measure, we find comparable reductions in forest cover in the same regions where cropland expands due to repeated dry anomalies. Second, we test the relationship in regions where yields are buffered from rainfall anomalies by irrigation infrastructure and find that the impact on cropland expansion is mitigated, providing further support for our results. Since cropland expansion is a significant driver of deforestation, these results have important implications for forest loss and environmental services.
12 Rijal, S.; Rimal, B.; Acharya, R. P.; Stork, N. E. 2021. Land use/land cover change and ecosystem services in the Bagmati River Basin, Nepal. Environmental Monitoring and Assessment, 193(10):651. [doi: https://doi.org/10.1007/s10661-021-09441-z]
Land use ; Land cover change ; Ecosystem services ; River basins ; Cultivated land ; Forest cover ; Biodiversity ; Carbon ; Sustainability ; Urbanization ; Models / Nepal / Bagmati River Basin
(Location: IWMI HQ Call no: e-copy only Record No: H050658)
(1.66 MB)
Delivery of ecosystem services is strongly affected by changes in the land use/land cover (LULC) of an area. In this study, we analyze spatiotemporal changes in LULC of the rapidly changing Bagmati River Basin (BRB) of Nepal during 1988–2018 using Landsat satellite images. We also quantify carbon storage in different physiographic regions and LULC classes using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model and assess economic valuation of carbon using the benefit transfer method. According to our analysis, there were increases in urban/built-up (247.5%), barren land (109.5%), shrub land (32.4%), and declines in forest cover (- 6.2%), cultivated land (- 4.1%), waterbodies (- 30.3%), sand (- 29.2%), and grass cover (- 10.6%) during the study period. As a result of these changes in LULC, carbon storage declined from 31.4 million tons year-1 in 1988 (worth 157.0 million USD) to 30.8 million tons year-1 (154.1 million USD) in 2018 with the total loss of 2.9 million USD. The largest decline in stored carbon was observed in Tarai and Dun valleys, from 6.8 to 6.5 million tons (- 1.4 million USD) followed by Churia, from 7.8 to 7.6 million tons (- 1.1 million USD). Increases in carbon storage were observed in urban/built-up and shrub land areas and declines in cultivated land, forest, barren land, waterbodies and grass land. The results of LULC change and estimated carbon stock in BRB provides a baseline for planners and policy makers to formulate appropriate plans to sustainably manage the region’s land cover and to mitigate carbon loss.
13 Bordoloi, R.; Das, B.; Tripathi, O. P.; Sahoo, U. K.; Nath, A. J.; Deb, S.; Das, D. J.; Gupta, A.; Devi, N. B.; Charturvedi, S. S.; Tiwari, B. K.; Paul, A.; Tajo, L. 2022. Satellite based integrated approaches to modelling spatial carbon stock and carbon sequestration potential of different land uses of Northeast India. Environmental and Sustainability Indicators, 13:100166. [doi: https://doi.org/10.1016/j.indic.2021.100166]
Carbon sequestration ; Carbon stock assessments ; Land use ; Land cover ; Satellite imagery ; Landsat ; Vegetation index ; Regression analysis ; Biomass ; Climate change mitigation ; Forest cover ; Remote sensing ; Modelling ; Simulation / India / Arunachal Pradesh / Assam / Manipur / Meghalaya / Mizoram / Nagaland / Sikkim / Tripura
(Location: IWMI HQ Call no: e-copy only Record No: H050887)
https://www.sciencedirect.com/science/article/pii/S2665972721000672/pdfft?md5=2b0c924ff6ef3156dbcfe3c57e940f61&pid=1-s2.0-S2665972721000672-main.pdf
https://vlibrary.iwmi.org/pdf/H050887.pdf
https://vlibrary.iwmi.org/pdf/H050887.pdf
(4.25 MB) (4.25 MB)
The study aims to estimate and predict the aboveground biomass, carbon stock and carbon sequestration potential of different land uses of Northeast India and relate these estimates with the land use changes. Many applications such as carbon stock and sequestration monitoring, forest degradation monitoring, and climate change mitigation, require precise and timely estimation of forest biomass. Although traditional field inventory can reliably estimate forest biomass, remote sensing is emerging as an alternate and fast approach to cover larger area with relative precision for biomass estimation. In this study, a combined approach of field inventory and Landsat OLI derived vegetation indices were used in spatial modelling of aboveground biomass and carbon stock in different land uses. A stepwise multilinear regression algorithm was used to derive the model that used Landsat derived NDVI, SAVI and ARVI as predicators. The predicted AGB ranged from 14.32 to 185.95 Mg ha-1 with an average of 148.78 Mg ha-1. The developed model that used combined vegetation indices showed correlation of R2 = 0.79 with an RMSE of 51.04 Mg ha-1. The present study also applied the empirical model (CO2FIX) to simulate the future scenario of carbon stock and carbon sequestration potential of the different land uses. The carbon stock potential of different land uses were 182.31 Mg ha-1, 158.91 Mg ha-1, 134.98 Mg ha-1, 169.26 Mg ha-1, 133.84, 89.95 Mg ha-1, 128.3 Mg ha-1 and 61.36 Mg ha-1 in Tropical forest, Subtropical forest, Temperate forest, Tropical plantation, Subtropical plantation, Temperate plantation, Shifting fallows and Agricultural land, respectively.
14 Tatlhego, M.; D'Odorico, P. 2022. Are African irrigation dam projects for large-scale agribusiness or small-scale farmers? Environmental Research Communications, 4(1):015005. [doi: https://doi.org/10.1088/2515-7620/ac2263]
Dams ; Irrigation programs ; Agribusiness ; Large scale systems ; Small scale farming ; Farmers ; Infrastructure ; Remote sensing ; Land use ; Forest cover ; Farm size ; Precipitation ; Economic development / Africa
(Location: IWMI HQ Call no: e-copy only Record No: H051051)
https://iopscience.iop.org/article/10.1088/2515-7620/ac2263/pdf
https://vlibrary.iwmi.org/pdf/H051051.pdf
https://vlibrary.iwmi.org/pdf/H051051.pdf
(1.07 MB) (1.07 MB)
The economic development of rural economies across the global south is often related to access to water and the development of water infrastructure. It has been argued that the construction of new dams would unleash the agricultural potential of African nations that are exposed to seasonal water scarcity, strong interannual rainfall variability, and associated uncertainties in water availability. While water security is often presented as the pathway to poverty alleviation and invoked to justify large dam projects for irrigation, it is still unclear to what extent small holders will benefit from them. Are large dams built to the benefit of subsistence farmers or of large-scale commercial agriculture? Here we use remote sensing imagery in conjunction with advanced machine learning algorithms to map the irrigated areas (or 'command areas') that have appeared in the surroundings of 18 major dams built across the African continent between 2000 and 2015. We quantify the expansion of irrigation afforded by those dams, the associated changes in population density, forest cover, and farm size. We find that, while in the case of nine dams in the year 2000 there were no detectable farming patterns, in 2015 a substantial fraction of the command area (ranging between 8.5% and 96.7%) was taken by large-scale farms (i.e., parcels >200 ha). Seven of the remaining 9 dams showed a significant increase in average farm size and number of farms between 2000 and 2015, with large-scale farming accounting for anywhere between 5.2% and 76.7% of the command area. Collectively, these results indicate that many recent dam projects in Africa are associated either with the establishment of large-scale farming or a transition from small-scale to mid-to-large scale agriculture.
15 Wickramasinghe, M. R. C. P.; Dayawansa, N. D. K.; Jayasiri, M. M. J. G. C. N.; De Silva, R. P. 2023. A study on external pressures of an ancient irrigation cascade system in Sri Lanka. Agricultural Systems, 205:103593. [doi: https://doi.org/10.1016/j.agsy.2022.103593]
Irrigation ; History ; Villages ; Tanks ; Systems ; Water quality ; Agrochemicals ; Runoff ; Land use change ; Climate variability ; Population growth ; Intensification ; Farming systems ; Water management ; Arid zones ; Agroclimatic zones ; Precipitation ; Water availability ; Sustainability ; Fertilizers ; Salinity ; Soil erosion ; Forest cover ; Water management / Sri Lanka / Anuradhapura / Maha Illuppallama / Mahakanumulla
(Location: IWMI HQ Call no: e-copy only Record No: H051615)
(3.87 MB)
CONTEXT: Village Tank Cascade Systems (VTCSs), which are ancient irrigation systems in Sri Lanka have undergone various pressures over time including climate variability, population growth, land use changes and agricultural intensification. VTCSs have provided irrigation and vital ecosystem services for generations, while facing these pressures. As external pressures have increased drastically over the last century, it is worthwhile to investigate VTCS's current capacity to tolerate pressures exerted on them while sustaining their functions.
OBJECTIVE: The objectives of this study were to (i) assess the pressures exerted on Mahakanumulla VTCS due to climate change, population growth, land use changes and agricultural practices, (ii) evaluate the impacts of the pressures on the system in terms of water quality and quantity.
METHODS: Rainfall data from 1906 to 2020 were analyzed to identify the rainfall trends over the last century. Land use maps were developed for 1910, 1979, 2002 and 2018. To identify current farming practices, a questionnaire survey was carried out targeting 357 respondents followed by field investigations. Environmental impacts due to pressures on the system were evaluated using water quantity estimations and quality tests.
RESULTS AND CONCLUSIONS: Paddy extent has increased from 6.3% to 20.2% while the homestead extent has increased from 1.6% to 11.5% during the last century. The lands used for sustainable shifting cultivation have encroached with permanent agricultural lands and human settlements. The runoff coefficient rose from 0.29 to 0.45, indicating a high outflow of water during rains and limiting water retention within the system. This is an indication of increasing water scarcity in dry periods due to limited recharge capacity. Although the system continues to function without significant water quality deterioration, agricultural activities can cause threats in the future. Hence, the system needs immediate attention in the context of proper land use planning, farmer awareness and integrated nutrient management at the cascade level to minimize these pressures exerted upon the system.
SIGNIFICANCE: Identifying and quantifying various pressures exerted on VTCSs is the fundamental step in setting management and mitigation plans. Project planners and policymakers need evidence-based information in this regard. Therefore, this study's findings and the research framework that may be extended to other VTCSs and similar systems are significant in creating a favorable policy environment and implementation programmes to reduce the risks the VTCSs are exposed to.
OBJECTIVE: The objectives of this study were to (i) assess the pressures exerted on Mahakanumulla VTCS due to climate change, population growth, land use changes and agricultural practices, (ii) evaluate the impacts of the pressures on the system in terms of water quality and quantity.
METHODS: Rainfall data from 1906 to 2020 were analyzed to identify the rainfall trends over the last century. Land use maps were developed for 1910, 1979, 2002 and 2018. To identify current farming practices, a questionnaire survey was carried out targeting 357 respondents followed by field investigations. Environmental impacts due to pressures on the system were evaluated using water quantity estimations and quality tests.
RESULTS AND CONCLUSIONS: Paddy extent has increased from 6.3% to 20.2% while the homestead extent has increased from 1.6% to 11.5% during the last century. The lands used for sustainable shifting cultivation have encroached with permanent agricultural lands and human settlements. The runoff coefficient rose from 0.29 to 0.45, indicating a high outflow of water during rains and limiting water retention within the system. This is an indication of increasing water scarcity in dry periods due to limited recharge capacity. Although the system continues to function without significant water quality deterioration, agricultural activities can cause threats in the future. Hence, the system needs immediate attention in the context of proper land use planning, farmer awareness and integrated nutrient management at the cascade level to minimize these pressures exerted upon the system.
SIGNIFICANCE: Identifying and quantifying various pressures exerted on VTCSs is the fundamental step in setting management and mitigation plans. Project planners and policymakers need evidence-based information in this regard. Therefore, this study's findings and the research framework that may be extended to other VTCSs and similar systems are significant in creating a favorable policy environment and implementation programmes to reduce the risks the VTCSs are exposed to.
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