Quantifcation of runoff as infuenced by morphometric characteristics in a rural complex catchment

This study addresses the critical scientific question of assessing the relationship between morphometric features and the hydrological factors that increase the risk of flooding in Kelantan River basin, Malaysia. Two hypotheses were developed to achieve this aim, namely: the alternate hypothesis (runoff, is influenced by morphometric characteristics in the study watershed) and the null hypothesis (runoff is not influenced by morphometric characteristics). First, the watershed was delineated into four major catchments, namely: Galas, Pergau, Lebir, and Nenggiri. Next, quantitative morphometric characters such as linear aspects, areal aspects, and relief aspects were determined on each of these catchments. Furthermore, HEC–HMS and flood response analyses were employed to simulate the hydrological response of the catchments. From the results of morphometric analysis, profound spatial changes were observed between runoff features of Kelantan River and the morphometric characteristics. The length of overflow that was related to drainage density and constant channel maintenance was found to be 0.12 in Pergau, 0.04 in both Nenggiri and Lebir, and 0.03 in Galas. Drainage density as influenced by geology and vegetation density was found to be low in all the catchments (0.07–0.24). Results of hydrological response indicated that Lebir, Nenggiri, Galas, and Pergau recorded a flood response factor of 0.75, 0.63, 0.40, and 0.05, respectively. Therefore, Lebir and Nenggiri are more likely to be flooded during a rainstorm. There was no clear indication with regard to the catchment that emerged as the most prevailing in all the morphological features. Hence, the alternate hypothesis was affirmed. This study can be replicated in other catchments with different hydrologic setup

Relationship between design floods and land use land cover (LULC) changes in a tropical complex catchment

Rainfall characteristics are directly related to the climate of a basin, but this can only be noticed after a long period. Human activities, such as deforestation, tend to play a major role in transforming the land use land cover (LULC). Knowledge of the relationship between design floods and LULC is important in modeling and designing watershed management strategies. A study was conducted in the Kelantan River basin, Malaysia, to determine the impact of past and present LULC changes on peak discharge and runoff volumes. To achieve this, the basin was delineated into four catchments (Galas, Pergau, Nenggiri, and Lebir) due to its size and increased precision. Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) model was calibrated based on December 20–30th, 2014, flood in Kelantan. Flood hydrographs corresponding to 1984, 2002, and 2013 LULC conditions were simulated, and relative changes in peak discharge and runoff volume were determined for different return periods (2, 5, 10, 20, 50, 100 years). Results of LULC analysis showed that Galas recorded highest deforestation (54.35%). When the four catchments were compared with respect to highest contribution of outlet peak discharge, Lebir under 2013 LULC condition was the highest with 2847.70 m3/s. This was followed by Nenggiri (2196.90 m3/s), Galas (1252.7 m3/s), and Pergau (328.7 m3/s), all under the 2013 LULC condition. Results of unit response approach applied based on 50-year return period to the catchments for ranking their sub-basins revealed that the novel fa index developed in this study provides a better way of ranking sub-basins with respect to their contribution to the outlet and therefore is recommended for use. Methodologies developed in this study may be useful to land use planners from around the world which when applied can provide alternatives that will minimize the adverse effects of floods

Long‑term hydrologic impact assessment of non‑point source pollution measured through land use/land cover (LULC) changes in a tropical complex catchment

The contribution of non-point source pollution (NPS) to the contamination of surface water is an issue of growing concern. Non-point source (NPS) pollutants are of various types and altered by several site-specific factors making them difficult to control due to complex uncertainties involve in their behavior. Kelantan River basin, Malaysia is a tropical catchment receiving heavy monsoon rainfall coupled with intense land use/land cover (LULC) changes making the area consistently flood prone thereby deteriorating the surface water quality in the area. This study was conducted to determine the spatio-temporal variation of NPS pollutant loads among different LULC changes and to establish a NPS pollutant loads relationships among LULC conditions and sub-basins in each catchment. Four pollutants parameters such as total suspended solids (TSS), total phosphorus (TP), total nitrogen (TN) and ammonia nitrogen (AN) were chosen with their corresponding event mean concentration values (EMC). Soil map and LULC change maps corresponding to 1984, 2002 and 2013 were used for the calculation of runoff and NPS pollutant loads using numeric integration in a GIS environment. Analysis of Variance (ANOVA) was conducted for the comparison of NPS pollutant loads among the three LULC conditions used and the sub-basins in each catchment. The results showed that the spatio-temporal variation of pollutant loads in almost all the catchments increased with changes in LULC condition as one moves from 1984 to 2013, with 2013 LULC condition found as the dominant in almost all cases. NPS pollutant loads among different LULC changes also increased with changes in LULC condition from 1984 to 2013. While urbanization was found to be the dominant LULC change with the highest pollutant load in all the catchments. Results from ANOVA reveals that statistically most significant (p < 0.05) pollutant loads were obtained from 2013 LULC conditions, while statistically least significant (p < 0.05) pollutant loads were obtained under 1984 LULC condition. This reveals the clear effect of LULC changes on NPS pollution. The findings of this study may be useful to water resource planners in controlling water pollution for future planning

Trend analysis of precipitation data in flood source areas of Kelantan river basin

Rainfall is one of the most important climatic elements that influence both the spatial and temporal water availability. Therefore, identification of its trend over years is vital for detection of extreme climatic changes. The purpose of this study is to investigate the variability of precipitation in flood source areas of Kelantan river basin by detecting precipitation flood changes in the temporal structure for the period of 1984-2014. A total of 17 rain gage stations with at least 25 years’ records in the temporal structure for the period 1984-2014 were selected. For the AMF data, 4 gauging stations were selected for the analysis. Mann-Kendall and Sen slope estimator tests were used to detect possible precipitation trend. This resulted in the detection of non-statistically significant trend in the annual maximum series of 24-hr precipitation in 12 of the 17 selected rain gauge locations and statistically significant trend in 5 locations for the period under study. Whereas, the AMF series signaled significance at 5% level in all the stations. This may be as a result of watershed characteristics such as land use changes soil, topography, of the study area which needs to be studied in detail

Trend analysis of precipitation data in flood source areas of Kelantan River Basin, Malaysia

Using the data of annual maximum series of 24-hour precipitation and the annual maximum flood (AMF) from Kelantan, the time series analysis of the river basin was analyzed for possible trend. The purpose of this study is to investigate the variability of precipitation in flood source areas of Kelantan river basin by detecting precipitation changes in the temporal structure for the period 1984-2014. Three rain gauge stations located upstream of the river basin (Jeli, Kuala Krai and Brook) were selected to represent the flood source areas where the annual maximum series of 24-hour precipitation data were taken. For the AMF data, four discharge gauging stations were selected (Kuala Krai, Galas, Pergau and Nenggiri) for analysis. Mann-Kendall and Sen slope estimator non-parametric tests were adopted for the methodology in order to detect possible precipitation trend. The application of this methodology resulted in the detection of no statistically significant trend in the annual maximum series of 24-hr precipitation in all the selected locations for the past 31 years. Whereas, the AMF series signalled significance at 5% level in all the stations where the AMF data was taken. This might be as a result of watershed characteristics such as land use changes, soil, topography that occurred in the study area which needs to be studied

Effect of Compaction Energy on Selected Physical and Hydraulic Properties of Soils Amended With Different Sources of Organic Matter

Soil compaction has been recognized as a severe problem in mechanized agriculture and influences soil properties and processes. A study evaluated the effect of different energy levels on selected properties of Alfisols treated with different sources of organic amendments. The treatments consisted of soils with compost (10 pots), cow dung (10 pots), and control. These were laid out in a completely randomized design and replicated two times. All pots (soil ± amendment) were saturated and allowed to drain freely for 24 hours and 48 hours, respectively, and compacted to 0, 75, 150, 225, and 300 Joules of energy. Bulk density (BD), penetration resistance (PR), saturated hydraulic conductivity (Ksat), particle size distribution (PSD), gravimetric moisture content (GMC), and moisture retention (MR) was determined from treated plots. Results obtained indicated that the soil is sandy. BD and PR were highest in control, with mean values of 1.803 g cm-3 and 1.762 kg F cm-2, respectively. Treatment with compost improved the BD and PR with lower mean values of 1.320 g cm-3 and 1.283 kg F cm-2 respectively, compared to cow dung and untreated control. With increasing energy inputs, there was a highly significant difference amongst the studied soil properties at all the energies at p<0.0001. Minimum tillage is recommended to reduce the stress caused by heavy energy inputs on these soil properties. The organic matter will directly contribute to plant nutrients such as nitrogen, phosphorus, and micronutrient

Review of studies on hydrological modelling in Malaysia

Hydrological models are vital component and essential tools for water resources and environmental planning and manage-ment. In recent times, several studies have been conducted with a view of examining the compatibility of model results with streamflow measurements. Some modelers are of the view that even the use of complex modeling techniques does not give better assessment due to soil heterogeneity and climatic changes that plays vital roles in the behavior of streamflow. In Malaysia, several public domain hydrologic models that range from physically-based models, empirical models and conceptual models are in use. These include hydrologic modeling system (HEC-HMS), soil water assessment tool (SWAT), MIKE-SHE, artificial neural network (ANN). In view of this, a study was conducted to evaluate the hydrological models used in Malaysia, determine the coverage of the hydrological models in major river basins and to identify the methodologies used (specifically model performance and evaluation). The results of the review showed that 65% of the studies conducted used physical-based models, 37% used empirical models while 6% used conceptual models. Of the 65% of physical-based modelling studies, 60% utilized HEC-HMS an open source models, 20% used SWAT (public domain model), 9% used MIKE-SHE, MIKE 11 and MIKE 22, Infoworks RS occupied 7% while TREX and IFAS occupy 2% each. Thus, indicating preference for open access models in Malaysia. In the case of empirical models, 46% from the total of empirical researches in Malaysia used ANN, 13% used Logistic Regression (LR), while Fuzzy logic, Unit Hydrograph, Auto-regressive inte-grated moving average (ARIMA) model and support vector machine (SVM) contributed 8% each. Whereas the remaining proportion is occupied by Numerical weather prediction (NWP), land surface model (LSM), frequency ratio (FR), decision tree (DT) and weight of evidence (WoE). Majority of the hydrological modelling studies utilized one or more statistical measure of evaluating hydrological model performance (R, R2, NSE, RMSE, MAE, etc.) except in some few cases where no specific method was stated. Of the 70 papers reviewed in this study, 16 did not specify the type of model evaluation criteria they used in evaluating their studies, 17 utilized only one method while 37 used two or more methods. NSE with 27% was found to be the most widely used method of evaluating model performance; R and RMSE came second with a percentage use 24% each. R2 (20%) was recorded as the third most widely used model evaluation criteria in Malaysia, MAE came fourth with 16% while PBIAS is the least with 11%.The findings of this work will serve as a guide to modelers in identifying the type of hydrological model they need to apply to a particular catchment for a particular problem. It will equally help water resources managers and policy makers in providing them with executive summary of hydrological studies and where more input is needed to achieve sustainable development