Trend analyses of hydro-meteorological data
Trend analyses of hydro-meteorological data are essential for the detection and understanding of changes in a rainfall-runoff process (Kliment et al., 2011). Detection of these changes in long term hydro-meteorological data is fundamental for the planning of future water resources and flood protection(Kliment & Matoušková, 2008). The hydro-meteorological trends can be induced by either land-use changes, river fluctuations, or climatic changes such as an increase and decrease of precipitation(Pfister et al., 2000). Climatic changes and anthropogenic activities are considered to be the leading causes of rainfall-runoff changes (Kliment et al., 2011). Cigizoglu et al. (2005) observed that streamflow is sensitive to precipitation changes and other factors since it is a critical part of the hydrologic cycle. Its variations have a direct impact on the water resources of a catchment. The changes in rainfall quantity and its frequency would alter the pattern of stream flows and demands (especially agriculture), streamflow distribution, soil moisture, and groundwater reserves. As such, trend analysis of rainfall and streamflow provide a better understanding of the problems associated with floods, droughts, and the water availability for various uses for the future water planning and management purposes and ecosystem conservations.
World Bank(2006) also found that unmitigated hydro-meteorological variability increases poverty rates and affect the growth potential of the country’s economy. Therefore, hydro-meteorological studies are critical for the social-economic development of the developing countries and the effective management and utilization of the water resources in the catchments. Malawi is one of the developing countries adversely affected by hydrological and meteorological variability. The climatic and hydrological variability has a direct impact on the country’s agri-based economy, which employs approximately 80% of the population. The country relies on both rain-fed agriculture and irrigation farming. A few studies have been done in the countries focusing on the spatial and temporal rainfall variability in different areas. For example, Ngongondo et al. (2011) analyzed temporal trends of rainfall in Malawi using Mann–Kendall and linear regression methods. The results revealed that most stations exhibited statistically non-significant decreasing rainfall trends for annual, seasonal, monthly, and the individual months from March to December.
Similarly, Kumbuyo et al. (2014) analyzed the spatial and temporal characteristics of rainfall in Malawi for 31 years, which found a strong inter-annual fluctuation of rainfall, with topography and location playing significant roles in the annual rainfall distribution. However, streamflow variability studies remain not much investigated in the country despite the essential role rivers play in the agriculture sector. For this reason, this study was carried out to assess the long term variability of the rainfall and streamflow in the Thuchila River, southern Malawi. Thuchila River is one of the many rivers that support the local people for small-scale agriculture and large irrigation schemes. Unfortunately, over the years, it has been affected by an increase in soil erosion and flash floods during the rainy season. Therefore, the study aimed to analyze the long-term trends and identify the change points in the hydro-meteorological variables. These findings will help the government and other stakeholders to make the right strategies for land and water resource management in the Thuchila catchment. It will also enable policymakers to formulate and implement effective policies to minimize the undesirable effects of future impacts on the streamflow pattern.