Impact of climate change over the hydrological system in a region can be identified through statistical characterization of hydrometerological parameters such as rainfall, temperature, humidity and evaporation. In order to understand the influence of climate change, statistical trend characteristics of rainy days, non-rainy days and evaporation rate in the Limbang River Basin (LRB) in Sarawak, Malaysia, Northern Borneo was assessed in the present research. Annual rainfall and monthly evaporation data, over a period of 46 years, (1970 - 2015) corresponding to three rain gauging stations, the Limbang DID, Ukong and Long Napir were used in the research. Linear regression model, Mann Kendall and Sen’s slope estimator techniques were applied to detect the statistical trends in rainy days and evaporation. A statistically significant increasing trend in annual rainy days was found at all the stations. Non-rainy days showed a statistically significant decreasing trend at Limbang DID and Ukong. Monthly evaporation rates showed an overall increasing trend and the greatest increasing trend in evaporation was observed in September (2.55 mm/year) for the Limbang DID and in December (2.61 mm/year) for Ukong. Evaporation measured at the Ukong station also showed a non-significant decrease during June and September. A comparison of the evaporation controlling meteorological variables such as rainfall, temperature and relative humidity indicates inter-influence at various strengths. Along with local precipitation characteristics, wind and fluctuation of atmospheric temperature over the region plays a vital role in increased rate of evaporation from the region. Overall, the analysis identified a statistically significant increasing trend in rainy days and evaporation in the LRB. The results of the present research can be used as critical planning data for micro and macro hydroelectric projects in the river basin.

A comparative analysis of trace metal (Cu, Pb, Fe, Mn, Zn, Cd, Ni and Co) concentration and physical parameters (pH, EC, TDS and DO) in rainwater samples collected from two major coastal cities in Malaysian Borneo (Sarawak state) were determined in the present research. Cumulative monthly rainwater samples were collected from the Limbang city and Miri city during October 2016–September 2017. Rainwater collected from the Limbang city shows slightly alkaline nature with a mean pH≥6.07 whereas the rainwater in Miri city is acidic(mean pH = 5.35). Trace metal concentration in rainwater collected from both locations shows slight variation. Mean concentration of trace metals in rainwater samples follows the decreasing order of Fe>Ni>Pb>Mn> Co>Cu>Zn>Cd and Fe>Ni>Pb>Mn>Zn>Co>Cu>Cd in Limbang city and Miri city respectively. Among the trace metals, Fe (1.09 and 0.98 mg/L) and Ni (0.15 and 0.13 mg/L) shows the highest mean concentration in rainwater samples collected from both locations and maximum concentration of trace metals are observed in rainwater samples collected from the Limbang city. Pearson’s correlation test explained the inter-relationship between the parameters whereas the factor analysis confirmed the contributing sources of trace metals (anthropogenic activities such as pollution from vehicles, petrochemical industries, forest biomass burning and dust particles from exposed land area) and its variation in the rainwater samples by showing a total variance of 80.18% with three factor components in the Limbang city and a variance of 93.11% with four factor components in Miri city. High Pb/Zn ratio also indicates the strong influence of anthropogenic activities present in the region. Backward air mass trajectory analysis supports the findings by indicating a contribution from combined marine and crustal sources of air mass trajectories reaching the sampling locations and is heavily controlled by prevailing monsoon characteristics of the region. Overall, it can be concluded that, the major source of trace metals in rainwater in this region is contributed by anthropogenic processes operated in the region.