Rainfall-runoff characteristics in a tropical forested catchment, Puchong, Selangor, Malaysia

This study aims to clarify the contributions of pre-event water to storm runoff using environmental tracers (dis‐ solved inorganic ions and stable isotopes) in a tropical forested catchment in Puchong, Selangor, Malaysia. We performed intensive sampling campaigns of stream water and throughfall for two storm events in July and November 2018. The discharge showed a low peak of 0.13 mm/h in event 1, with 18 mm of total rainfall, whereas event 2, with 50 mm of total rainfall, showed a quick discharge peak of 1.17 mm/h and a slow recovery of 0.39 mm/h. The nitrate concentration in the stream water during event 2 was higher than that in event 1. The temporal variations in nitrate ions indicate that subsurface water provided a dominant storm‐ flow in event 2. Hydrograph separations using silicate as a tracer revealed that pre-event water was the dominant com‐ ponent of the storm hydrograph (58–98%). Our results sug‐ gest that pre-event water plays an essential role in storm runoff of headwaters in humid tropical regions

Assessment of streamflow simulation for a tropical forested catchment using dynamic TOPMODEL—Dynamic fluxEs and ConnectIvity for Predictions of HydRology (DECIPHeR) framework and Generalized Likelihood Uncertainty Estimation (GLUE)

Rainfall runoff modeling has been a subject of interest for decades due to a need to understand a catchment system for management, for example regarding extreme event occurrences such as flooding. Tropical catchments are particularly prone to the hazards of extreme precipitation and the internal drivers of change in the system, such as deforestation and land use change. A model framework of dynamic TOPMODEL, DECIPHeR v1—considering the flexibility, modularity, and portability—and Generalized Likelihood Uncertainty Estimation (GLUE) method are both used in this study. They reveal model performance for the streamflow simulation in a tropical catchment, i.e., the Kelantan River in Malaysia, that is prone to flooding and experiences high rates of land use change. Thirty-two years’ continuous simulation at a daily time scale simulation along with uncertainty analysis resulted in a Nash Sutcliffe Efficiency (NSE) score of 0.42 from the highest ranked parameter set, while 25.35% of the measurement falls within the uncertainty boundary based on a behavioral threshold NSE 0.3. The performance and behavior of the model in the continuous simulation suggests a limited ability of the model to represent the system, particularly along the low flow regime. In contrast, the simulation of eight peak flow events achieves moderate to good fit, with the four peak flow events simulation returning an NSE > 0.5. Nonetheless, the parameter scatter plot from both the continuous simulation and analyses of peak flow events indicate unidentifiability of all model parameters. This may be attributable to the catchment modeling scale. The results demand further investigation regarding the heterogeneity of parameters and calibration at multiple scales

Land use change using geospatial techniques in upper Prek Thnot watershed in Cambodia

Monitoring of land use change is crucial for sustainable resource management and development planning. Up-to-date land use change information is important to understand its pattern and identify the drivers. Remote sensing and geographic information system (GIS) have proven as a useful tool to measure and analyze land use changes. Recent advances in remote sensing technology with digital image processing provide unprecedented possibilities for detecting changes in land use over large areas, with less costs and processing time. Thus, the objective of this study was to assess the land use changes in upper Prek Thnot watershed in Cambodia from 2006 until 2018. Geospatial tools such as remote sensing and GIS were used to process and produce land use maps from Landsat 5 TM, Landsat 7 ETM+ and Landsat 8. The post-classification comparison was conducted for analysing the land use changes. Results show forest area was greatly decreased by 1,162.06 km2 (33.67%) which was converted to rubber plantation (10.55 km2), wood shrub (37.65 km2), agricultural land (1,099.71 km2), built-up area (17.76 km2), barren land (3.65 km2), and water body (14.69 km2). Agricultural land increased by 1,258.99 km2 (36.48%), while wood shrub declined by 161.88 km2 (4.69%). Rubber plantation, built-up area, barren land, and water bodies were increased by 10.55 km2 (0.31%), 33.64 km2 (0.97%), 4.87 km2 (0.14%) and 15.89 km2 (0.46%), respectively. The decrease of forest and wood shrub had resulted due to population growth (1.8% from 2008 to 2019) and land Monitoring of land use change is crucial for sustainable resource management and development planning. Up-to-date land use change information is important to understand its pattern and identify the drivers. Remote sensing and geographic information system (GIS) have proven as a useful tool to measure and analyze land use changes. Recent advances in remote sensing technology with digital image processing provide unprecedented possibilities for detecting changes in land use over large areas, with less costs and processing time. Thus, the objective of this study was to assess the land use changes in upper Prek Thnot watershed in Cambodia from 2006 until 2018. Geospatial tools such as remote sensing and GIS were used to process and produce land use maps from Landsat 5 TM, Landsat 7 ETM+ and Landsat 8. The post-classification comparison was conducted for analysing the land use changes. Results show forest area was greatly decreased by 1,162.06 km2 (33.67%) which was converted to rubber plantation (10.55 km2), wood shrub (37.65 km2), agricultural land (1,099.71 km2), built-up area (17.76 km2), barren land (3.65 km2), and water body (14.69 km2). Agricultural land increased by 1,258.99 km2 (36.48%), while wood shrub declined by 161.88 km2 (4.69%). Rubber plantation, built-up area, barren land, and water bodies were increased by 10.55 km2 (0.31%), 33.64 km2 (0.97%), 4.87 km2 (0.14%) and 15.89 km2 (0.46%), respectively. The decrease of forest and wood shrub had resulted due to population growth (1.8% from 2008 to 2019) and land conversion for agricultural purposes. Hence, this study may provide vital information for wise sustainable watershed’s land management, especially for further study on the effect of land use change on runoff in this area

Habitat selection of Dendrocygna javanica in heterogeneous lakes of Malaysia

Monitoring the habitat selection of lesser whistling Duck (Dendrocygna javanica) is highly crucial for species conservation and management. In this study, habitat selection of D. javanica in 14 heterogeneous lakes (direct visual observation and point sampling technique) and foraging ecology (scan through method) was investigated through April-September, 2016. It was observed that lake Belibis L1 was heavily preferred by D. javanica (i.e., 166.16 individuals) and less preferred lake Kemoning L11 (i.e., 0.2 individuals). However, three lakes i.e., Seroja L2, Telipok L3 and Drift Wood L4 were completely avoided by D. javanica (i.e., no individual was observed) during the study period. The highest pH value was observed in lake Grebe L8 (September 2016; 8.9) and the lowest one in lake Seroja L2 (May 2016; 6.3). Likewise, the highest mean water temperature was recorded in lake Senduduk L6 (June 2016; 32.9 C°) and the lowest one was determined in lake Grebe L8 (July 2016; 20.7 C°). Multivariate analysis i.e., correlation matrix identified multi-collinearity relationship between relative abundance of lesser whistling Duck with Water Level Fluctuation (WLF),Water Quality Index (WQI), Lake Size (LS) and Normalized Difference Vegetation Index (NDVI). Inter-specific variation analysis showed that habitat selection by D. javanica occurs at a species-specific level in responses to changes inenvironmental factors. For example, the highest abundance occurred at minimum water depth (i.e., slope ± SE=-0.004 ± 0.309; P<0.001) while the lowest one at water quality index (slope ± SE=0.069±0.309; P<0.001), lake size (slope ± SE=0.028 ± 13.731; P<0.001), and NDVI (slope ± SE= 6.273 ± 13.731; P<0.001) respectively. This study indicated that habitat type and composition has a great effect on the population of D. javanica. Also it shows that D. javanica preferred shallow lakes rich with aquatic plants and aquatic invertebrates

Water quality characteristics in relation to mangrove disturbance levels

Mangroves are an important ecosystem that provides environmental protection and play a significant role in economic activity especially for fisheries and charcoal products. The mangrove ecosystem offers carbon absorption and shoreline protection against natural events. However, land conversion and poor land use management resulted in excessive pollution that might affect mangrove health, particularly hydrology. Variation in hydrological characteristics might be influenced by climate change which also affects the extreme events and climate cycles. Matang Mangrove Forest Reserve (MMFR) is a large contiguous mangrove forest in Peninsular Malaysia (40,466ha) known for its excellent management of timber. Aerial images were used to classify the different mangrove disturbance levels (e.g. least disturbed, moderately disturbed and mostly disturbed) and relates the conditions with water quality. Water quality data from 2004 to 2013 were acquired from the Department of Environment (DOE). The temporal variation of water quality characteristics was analysed in relation to the classification of mangrove disturbance levels. The finding indicates that three mangrove areas have different water quality conditions corresponding to its disturbance levels. This will be used to facilitate meteorological, hydrological and ecological assessment in mangroves for better management of mangroves in the future

A preliminary investigation on water quality of water courses in oil palm smallholdings converted from peat swamp and mangrove forests

Oil palm smallholdings had been extensively established at the expense of peat swamp or mangrove forests. This study was conducted at peat swamp forest converted (PF) and mangrove forest-converted (MF) sites in Tanjung Karang, Selangor. Dissolved oxygen (DO), pH, temperature, electric conductivity (EC), turbidity, salinity and total dissolved solids (TDS) were measured with corresponding water levels at 25 stations in each study site. Kruskal-Wallis Analysis of Variance was used to compare the means of each water quality parameter for both study sites while the Spearman’s correlation tests were used to detect any collinearity between parameters. The preliminary results indicated that EC, salinity, pH and TDS were significantly higher in MF compared to PF (Kruskal Wallis p < 0.001) due to the high salt concentration in MF and low pH in PF. Although both study sites were converted to oil palm about 50 years ago, the water quality measured suggest that the levels were much influenced by the original land cover

Assessing river stability and hydraulic geometry of fluvial river in Malaysia

The fluvial geomorphological descriptions of rivers are very important to maintain the natural presence through studying the river stability and sediment transport research. Lack of knowledge on fluvial characteristics will lead to improper water resources management in long term. This research was focused to determine the fluvial river characteristics, to identify the management interpretation of the river stability and to assess the variation of flow regime and equilibrium geometry. The assessment of Rasau River was taken at different morphological appearance such as bedrock, cascade, pool, plain and step-pool. At station data collection were river width, velocity, bed materials, slope of the channel, bank slope and longitudinal profile. Classification of Rasau River were found that RCS1, RCS2, RCS3, RCS4, RCS5, RCS6, RCS7, RCS8 are classified as B4, B3, G4, F3b, F2b, E5b, B5 and B5 respectively. Based on the river classification, the conditions of cross sectionsRCS4and RCS5 are not stable with sediment load low to very high and the energy of water to the stream also shows low to moderate. Low energy of water flow can lower sediment transport rates thus in long term will cause aggradation and channel narrowing. At RCS1,2, 3, 6, 7 and 8 are classified as a stable cross section with bank vegetation as a component of the cross-section stability. The energy of water is in a range of high to moderate and the sediment load is in a range of low to moderate. On the assessment of the equilibrium geometry, Width,B = aQb, Depth, D = cQf, and Velocity, v = kQm. This study was found that hydraulic geometry equations for Rasau River are B = 12.3Q0.2, D = 0.9Q0.5, V = 0.09Q0.3. It was successfully verified that the hydraulic geometry parameters satisfy continuity equation where the summation of the exponents and the multiplication of the coefficients must give a mathematical value of unity thus specify that Q = BDV. The coefficient of width (a value) shows the highest, this shows that the widening of the river can increase the significant change of the flow rate of the river

A preliminary investigation on water birds and their relation with flood-control drain water quality in oil palm smallholdings

Human modified landscapes such as oil palm planted areas can sustain water bird communities. This study aimed at quantifying the diversity of water birds at aquatic habitats in oil palm smallholdings in Tanjung Karang, Selangor. Seven water quality characteristics were measured, namely, pH, dissolved oxygen (DO), total dissolved substance (TDS), water temperature, salinity, conductivity and turbidity. Ground vegetation cover, stream width, water level and stream velocity were also measured. Twenty five line transects were established within the peat swamp forest-converted (PF) and mangrove forest–converted (MF) oil palm smallholdings. Between March and April 2013, a total of 315 water birds (seven species - six residents and one migratory species) were recorded. The species diversity of water birds was higher in MF than PF. At PF, species richness increased with water level and TDS, but decreased with salinity. At MF, species richness decreased with water level and turbidity. Flood-control drains and water quality are important for water bird conservation in oil palm planted areas

Physicochemical properties as driver of Odonata diversity in oil palm waterways

Large-scale oil palm agriculture has caused deforestation in the tropics, but also degrades stream water quality and reduces aquatic biodiversity. Though the outcomes of industrial-scale oil palm plantations for biodiversity have been explored extensively, the consequences of small-scale oil palm agriculture for freshwater macroinvertebrate fauna are poorly understood. Here, we explored the impacts of small-scale oil palm agriculture on aerial adult Odonata (the dragonflies and damselflies), which, due to their inherent sensitivity to habitat degradation, represent useful indicators of wider ecosystem health. We surveyed riparian corridors of man-made waterways in natural habitats converted into agricultural lands in both peat swamp and mangrove forest, comprising a total of 60 sampling units across a region of Peninsular Malaysia where such small-scale agricultural practices are widespread. We hypothesized that physicochemical water quality of oil palm waterways together with riparian vegetation influence Odonata species richness and composition. Our results revealed that Odonata species richness increased with dissolved oxygen, water temperature and vegetation cover, but decreased with water level, pH, and total dissolved solids. Species composition was influenced by both dissolved oxygen and pH. The present study provides valuable insights into the effects of small-scale oil palm agriculture for water quality of associated aquatic habitats, and subsequent responses of adult Odonata. Therefore, smallholders should reduce the use of chemical pesticides and fertilizers to improve the conservation value of oil palm waterways for both Odonata and aquatic fauna more generally, in order to be certified as biodiversity-friendly agriculture