IMPACT OF CHANGES IN CLIMATE AND LAND USE ON THE FUTURE STREAMFLOW FLUCTUATION: CASE STUDY MERANGIN TEMBESI WATERSHED, JAMBI PROVINCE, INDONESIA

There is a growing concern on a global scale that the world should transition towards the utilisation of energy-efficient technologies. Hydropower plays a very significant part in the fight against climate change, and as a result, it lessens the impact that climate changewill have on our ability to achieve the Sustainable Development Goals (SDGs). Both the effectiveness of hydropower generation and the amount of streamflow are impacted by climate change as well as land use and land cover (LULC). Accordingly, the purpose of this study is to conduct a literature review on the topic of the past and future effects of climate, land use, and land cover changes on hydropower generation. This review will be based on the entries found in a number of reliable databases. A systematic literature review was carried out to analyse how LULC and climate change will affect hydropower generation and development. The research was based on 158 pieces of relevant literature that had been reviewed by experts and indexed in Scopus, Google Scholar, and ScienceDirect. The review was carried out to determine three goals in mind: the impact of climate change on hydropower generation and development; the impact of climate change on streamflow; and the combined impact of changes in climate and changes in LULC on hydropower. The findings bring to light the primary factors contributing to climate change as well as shifts in LULC which are essential to the generation of hydropower on all scales. The study identifies factors such as precipitation, temperature, floods, and droughts as examples of climate change. Deforestation, afforestation, and urbanisation are identified as the primary causes of changes in LULC over the past several decades. These changes have a negative impact on the generation and development of hydropower.

Climate and land use land cover (LULC) changes play a vital role in the hydrology of any river basin. This study was aimed to investigate the impact of climate and LULC changes on streamflow in the Kunhar river basin, Pakistan. The Soil and Water Assessment Tool (SWAT), calibrated on a monthly basis, was used as a hydrological model to study the impact of climate and LULC changes on the streamflow. The change in average annual runoff due to LULC was increased but not significant; on the other hand, the flow was decreased by 24 m3/s (20%) as compared to the baseline (122 m3/s), due to climate change. On the seasonal and monthly scale, a difference emerged between high and low flows; high flows were increasing and low flows were decreasing in the wet and dry seasons, respectively, due to LULC changes. However, due to climate change, the seasonal and monthly runoffs were decreased significantly. Problems such as depletion in surface water and environmental flow during the dry season were more prominent due to the changes in the streamflow. These problems can be mitigated by afforestation in the bare lands and grasslands and taking structural measures to conserve the water in the high flow season for later use.

Water shortage has become a major challenge in many parts of the world due to climate change and socio-economic development. Allocating water is critical to meet human and ecosystem needs in these regions now and in the future. However, water allocation is being challenged by uncertainties associated with climate change and socio-economic development. This thesis aims to assess the combined effects of climate change and socio-economic development on water supply and demand in the Pearl River Basin (PRB) in China, and identify water allocation plans, which are robust to future climate change and socio-economic development. To do so, the impact of climate change on future water availability is first assessed. Next, different model frameworks are developed to identify robust water allocation plans for improving reservoir management, ensuring sufficient flow into the delta to reduce salt intrusion, and providing sufficient freshwater for human and industrial consumption under future climate change and socio-economic development. Results show that water availability is becoming more variable throughout the basin due to climate change. River discharge in the dry season is projected to decrease throughout the basin. For a moderate climate change scenario (RCP4.5), low flows reduce between 6 and 48 % depending on locations. For a high climate change scenario (RCP8.5), the decreases of low flows can reach up to 72%. In the wet season, river discharge tends to increase in the middle and lower reaches and decreases in the upper reach of the Pearl River Basin. The variation of river discharge is likely to aggravate water stress. Especially the reduction of low flow is problematic as already the basin experiences water shortages during the dry season in the delta. The model frameworks developed in this study not only evaluate the performance of existing water allocation plans in the past, but also the impact of future climate change on robustness of previous and newly generated water allocation plans. The performance of the four existing water allocation plans reduces under climate change. New water allocation plans generated by the two model frameworks perform much better than the existing plans. Optimising water allocation using carefully selected state-of-the-art multi-objective evolutionary algorithms in the Pearl River Basin can help limit water shortage and salt intrusion in the delta region. However, the current water allocation system with six key reservoirs is insufficient in maintaining the required minimum discharge at two selected gauge stations under future climate change. More reservoirs, especially in the middle and lower reaches of the Pearl River, could potentially improve the future low flow into the delta. This study also explored future water shortage in the Pearl River Basin under different water availability and water use scenarios. Four different strategies to allocate water were defined. These water allocation strategies prioritize upstream water use, Pearl River Delta water use, irrigation water use, and manufacturing water use, respectively. Results show that almost all the regions in the Pearl River Basin are likely to face temporary water shortage under the four strategies. The increasing water demand contributes twice as much as the decreasing water availability to water shortage. All four water allocation strategies are insufficient to solve the water scarcity in the Pearl River Basin. The economic losses differ greatly under the four water allocation strategies. Prioritizing the delta region or manufacturing production would result in lower economic losses than the other two strategies. However, all of them are rather extreme strategies. Development of water resources management strategies requires a compromise between different water users. Optimization algorithms prove to be flexible and useful tool in adaptive water resources allocation for providing multiple approximate Pareto solutions. In addition, new technologies and increasing water use efficiency will be important to deal with future water shortage in the Pearl River Basin.

Impacts of combined land-use and climate change on streamflow in two nested catchments in the Southeastern United States

The Batanghari River flows from the province of West Sumatra into the West Coast of Jambi, with the main river extending up to 870 km. Also, the Batanghari watershed Land use changes have shown a decreasing forest cover and an increasing agricultural area. Therefore, this study aims to calculate the impact of land use and climate change on water and sediment yield using Soil and Water Assessment Tools (SWAT) hydrological modeling. Land-use change analysis was performed with projections in 2040 while, near future and future climate projections under Representative Concentration Pathway (R.C.P.) 4.5 and 8.5 were used for global climate change scenarios. The results show a changing pattern of growing agricultural area and decreasing forest area in 1990, 1997, 2005, 2015, and 2040. SWAT hydrological model used for the simulation was calibrated automatically with SWAT-CUP and the results were validated on good criteria. The sensitivity analysis results showed that effective hydraulic conductivity in main channel alluvium (CH_K2) and Base flow alfa factor (Alfa_BF) formed the most sensitive parameters for discharge. Furthermore, the model simulation showed an increase in surface runoff and a decrease in lateral flow and base flow due to land-use changes, which increased sediment loading over time. The impact of climate change on water and sediment yield increased the average flow discharge ratio, resulting in more frequent droughts and floods events.

This paper evaluates the possible impacts of climate change and land use change and its combined effects on soil loss and net soil loss (erosion and deposition) in the Mae Nam Nan sub-catchment, Thailand. Future climate from two general circulation models (GCMs) and a regional circulation model (RCM) consisting of HadCM3, NCAR CSSM3 and PRECIS RCM ware downscaled using a delta change approach. Cellular Automata/Markov (CA_Markov) model was used to characterize future land use. Soil loss modeling using Revised Universal Soil Loss Equation (RUSLE) and sedimentation modeling in Idrisi software were employed to estimate soil loss and net soil loss under direct impact (climate change), indirect impact (land use change) and full range of impact (climate and land use change) to generate results at a 10 year interval between 2020 and 2040. Results indicate that soil erosion and deposition increase or decrease, depending on which climate and land use scenarios are considered. The potential for climate change to increase soil loss rate, soil erosion and deposition in future periods was established, whereas considerable decreases in erosion are projected when land use is increased from baseline periods. The combined climate and land use change analysis revealed that land use planning could be adopted to mitigate soil erosion and deposition in the future, in conjunction with the projected direct impact of climate change.

This paper studies the impact of climate change on agricultural productivity in Bangladesh for the period 1975-2008 for 23 regions. First, the study relies on descriptive statistics to explore the long term changes at both country and local level in climatic variables such as temperature, rainfall, humidity and sunshine. Second, it uses regression models to estimate the impact of climate change on agricultural productivity. Unlike the existing literature, this study exploits within-region time series variations (regional fixed effect) to estimate the impact of long term changes in climatic variables on agricultural productivity in order to control for regional differences, both observed and unobserved. Descriptive statistics shows that overall average, maximum and minimum temperatures in the dry and wet seasons have increased in recent years. Fluctuations in the minimum and maximum temperatures have also increased. Average rainfall in the dry season has increased substantially with greater fluctuations. Regression results show that an increase in the average minimum temperature in the dry season by one unit increases per acre rice output by 3.7% to 11.6%. Average minimum temperature in the wet season is also found to have a negative and significant impact even after controlling for region and year fixed effects. Standard deviations of maximum temperature in both dry and wet seasons are found to have a negative impact on agricultural productivity, though the impact in the wet season loses its significance after controlling for the year fixed effect. In the case of Boro rice, the only variable that is significant after controlling region and year specific heterogeneity is the standard deviation of maximum temperature in the Boro season. The regression results indicate that long term changes in means and standard deviations of the climatic variables have differential impacts on the productivity of rice and thus the overall impact of climate change on agriculture is not unambiguous. We found that when regional variations are considered, it significantly changes the sign and size of the estimates. The impact differs significantly with the choice of weather variables – mean vs. standard deviation (fluctuation), minimum vs. maximum, dry vs. wet seasons. For example, the impact of an increase in one unit of minimum temperature and maximum temperature on rice productivity are different in the same wet season. The choice of weather variables should therefore be driven by scientific knowledge, which the current economics literature lacks.

In the context of global climate change and intensifying human activities, effective management of urban ecosystem services (ESs) is crucial for achieving sustainable development goals. Urbanization-induced land use change and climate change are two primary drivers altering UESs. However, previous studies have predominantly focused on historical urban expansion and climate change effects on UESs, leaving future evolution scenarios and their relative impacts underexplored. This study investigates the Pearl River Delta urban agglomeration as a case study area, examining the relative impacts of land use and climate change on five UESs: water yield (WY), soil conservation (SC), water purification (WP), urban flood risk mitigation (FM), and urban cooling (UC). The results revealed that all five ecosystem services exhibited high values in the peri-urban areas and low values in the urban core of the Pearl River Delta. WY, FM, and UC showed an overall increasing trend, while SC and WP exhibited fluctuating trends from 1990 to 2050. Changes in SC were predominantly influenced by climate change, accounting for 76.24% of the total area, whereas WY, WP, FM, and UC services were primarily affected by land use change, accounting for over 67.16% of the area. In the future scenarios of 2035 and 2050, the impact of climate change on soil conservation varied the most across different Shared Socio-economic Pathway (SSP) scenarios. The impact of land use change on WY, WP, FM, and UC exhibited the most significant differences across urban areas, indicating a high sensitivity of urbanization-induced ecosystem services to human disturbances.

The Lake Victoria basin’s expanding population is heavily reliant on rainfall and river flow to meet their water needs, making them extremely vulnerable to changes in climate and land use. To develop adaptation and mitigation strategies to climate changes it is urgently necessary to evaluate the impacts of climate change on the quantity of water in the rivers that drain into Lake Victoria. In this study, the semi-distributed hydrological SWAT model was used to evaluate the impact of current land use and climate changes for the period of 1990–2019 and assess the probable future impacts of climate changes in the near future (2030–2060) on the Simiyu river discharge draining into Lake Victoria, Northern Tanzania. The General Circulation Model under RCPs 4.5, 6.0 and 8.5 predicted an increase in the annual average temperature of 1.4 °C in 2030 to 2 °C in 2060 and an average of 7.8% reduction in rainfall in the catchment. The simulated river discharge from the hydrological model under RCPs 4.5, 6.0 and 8.5 revealed a decreasing trend in annual average discharge by 1.6 m3/s from 5.66 m3/s in 2019 to 4.0 m3/s in 2060. The increase in evapotranspiration caused by the temperature increase is primarily responsible for the decrease in river discharge. The model also forecasts an increase in extreme discharge events, from a range between 32.1 and 232.8 m3/s in 1990–2019 to a range between 10.9 and 451.3 m3/s in the 2030–2060 period. The present combined impacts of climate and land use changes showed higher effects on peak discharge at different return periods (Q5 to Q100) with values of 213.7 m3/s (Q5), 310.2 m3/s (Q25) and 400.4 m3/s (Q100) compared to the contributions of climate-change-only scenario with peak discharges of 212.1 m3/s (Q5), 300.2 m3/s (Q25) and 390.2 m3/s (Q100), and land use change only with peak discharges of 295.5 m3/s (Q5), 207.1 m3/s Q25) and 367.3 m3/s (Q100). However, the contribution ratio of climate change was larger than for land use change. The SWAT model proved to be a useful tool for forecasting river discharge in complex semi-arid catchments draining towards Lake Victoria. These findings highlight the need for catchment-wide water management plans in the Lake Victoria Basin.

기후변화와 토지이용변화는 유역의 수문순환의 변화를 초래하여 가용수자원의 변화를 야기 시킨다. 본 연구에서는 안성천 (<TEX>$371.1km^2$</TEX>) 유역을 대상으로 SWAT (Soil and Water Assessment Tool)모형을 이용하여 미래기후변화와 토지이용변화가 유출특성에 미치는 영향을 분석하고자 하였다. 미래 기후자료는 IPCC 제 5차 기후변화 평가보고서에서 생산된 RCP (Representative Concentration Pathway, 대표농도경로)기반의 기후변화 시나리오 중 기상청에서 제공한 RCP 4.5와 8.5 시나리오(한반도 영역; 12.5km)를 이용하였다. 기준 년과 비교한 결과 RCP 8.5의 2080s (2060-2099)에서 평균온도가 <TEX>$4.2^{\circ}C$</TEX> 상승하였으며, 강우량은 최고 21.2% 증가하는 것으로 나타났다. 토지이용변화 추세는 CLUE-s (Conservation of Land Use and its Effects at Small regional extent)모형을 이용하여 예측되었고, 도시 면적 증가에 따른 3가지 시나리오(Linear, Exponential, Logarithmic)를 적용한 안성천 유역의 미래(2040s, 2080s) 토지이용도를 구축하였다. 각각의 시나리오에서 도시면적 비율은 2100년에 9.4%, 20.7%, 35%로 예측되었다. 기후변화만을 고려하였을 때 증발산량과 총 유출량은 RCP 8.5의 2080s에서 최고 20.6%, RCP 4.5의 2080s에서 최고 25.7% 증가하는 것으로 나타났다. 또한 토지이용변화만을 고려한 경우 증발산량과 총 유출량은 최고 3.7%, 2.9% 증가하는 것으로 나타났다. 토지이용과 기후변화 시나리오를 모두 적용한 경우 증발산량과 총 유출량은 RCP 8.5 2080s의 Linear 토지이용변화 시나리오에서 최고 19.2% 증가하였으며, RCP 4.5 2080s의 Exponential 토지이용변화 시나리오에서 최고 36.1%증가하는 것으로 나타났다. 본 연구를 통해 미래의 유역 수문환경조건 변화에 따른 수자원을 정량적으로 파악할 수 있을 것으로 기대된다. Climate and land use changes have impact on availability water resource by hydrologic cycle change. The purpose of this study is to evaluate the hydrologic behavior by the future potential climate and land use changes in Anseongcheon watershed (<TEX>$371.1km^2$</TEX>) using SWAT model. For climate change scenario, the HadGEM-RA (the Hadley Centre Global Environment Model version 3-Regional Atmosphere model) RCP (Representative Concentration Pathway) 4.5 and 8.5 emission scenarios from Korea Meteorological Administration (KMA) were used. The mean temperature increased up to <TEX>$4.2^{\circ}C$</TEX> and the precipitation showed maximum 21.2% increase for 2080s RCP 8.5 scenario comparing with the baseline (1990-2010). For the land use change scenario, the Conservation of Land Use its Effects at Small regional extent (CLUE-s) model was applied for 3 scenarios (logarithmic, linear, exponential) according to urban growth. The 2100 urban area of the watershed was predicted by 9.4%, 20.7%, and 35% respectively for each scenario. As the climate change impact, the evapotranspiration (ET) and streamflow (ST) showed maximum change of 20.6% in 2080s RCP 8.5 and 25.7% in 2080s RCP 4.5 respectively. As the land use change impact, the ET and ST showed maximum change of 3.7% in 2080s logarithmic and 2.9% in 2080s linear urban growth respectively. By the both climate and land use change impacts, the ET and ST changed 19.2% in 2040s RCP 8.5 and exponential scenarios and 36.1% in 2080s RCP 4.5 and linear scenarios respectively. The results of the research are expected to understand the changing water resources of watershed quantitatively by hydrological environment condition change in the future.

The impact of climate change and human activities poses significant challenges in the tropical region of Southeast Asia, specifically within the Mun-Chi River Basin, the largest tributary of the Mekong River in Thailand. The bias-corrected MPI-ESM1-2-LR, the most appropriate Global Climate Model (GCM) under the Coupled Model Intercomparison Project Phase 6 (CMIP6) for projecting Mun-Chi River flow, represent future climate variations in the basin. The analysis reveals forthcoming transformations in future land use, with cropland areas transitioning into forests and urban areas. The projected annual streamflow contributing to the Lower Mekong River is expected to increase by 1.14% to 3.49% in 2023-2035 and 1.84% to 4.26% in 2036-2050, with 67.17% attributed to climate change and 32.83% to land-use change. Temporal variations in the future flow regime reveal a wetter wet season and a drier dry season in this catchment. During the wet season, streamflow is projected to rise by 4.97% to 17.67% in 2023-2035 and 9.97% to 24.08% in 2036-2050. In contrast, the dry season is expected to experience a decrease of -2.69% to -9.15% in 2023-2035 and -6.28% to -17.10% in 2036-2050. These seasonal contrasts suggest a potential increase in extreme hydrological events, presenting challenges for efficient water resource management in this watershed and downstream countries. Consequently, effective water regulation and land-use policies are deemed crucial for sustainable management in the Mun-Chi River Basin.

Whereas normal water flow in a catchment is necessary for all forms of life, the hydrologic systems in the Sigi catchment is susceptible to land use and climate changes. Over the past three decades, water balance of the Sigi Catchment has indicated changes with unknown forms and magnitudes. To uncover the dynamics, this study used SWAT model to simulate water balance to a separate and combined impact of land-use and climate change. SWAT simulation showed good performance with NSE=0.58 and R2=0.67 for calibration, and NSE=0.56 and R2=0.64 for validation periods. Land use change scenarios indicated increase in surface runoff by 16.1mm, while base flow and water yield decreased by 23.1mm and 7.2mm, respectively. Climate change scenarios indicated an increase in surface runoff by 29.9mm, while base flow and water yield decreased by 36.1mm and 14.2mm, respectively. The combined land use and climate change scenarios indicated increase of surface runoff by 19.0mm, and decrease in base flow and water yield by 29.7mm and 10.7mm, respectively. From the study, it is clearly that the impacts of climate change on water balance components of the Sigi catchment are larger than land use change. Owing to the dilemma facing water resources in this era of climate change, long-term planning that balance households’ livelihood options and water resources management option is needed.

The application of species distribution modeling in deserts is a useful tool for mapping species and assessing the impact of human induced changes on individual species. Such applications are still rare, and this may be attributed to the fact that much of the arid lands and deserts around the world are located in inaccessible areas. Few studies have conducted spatially explicit modeling of plant species distribution in Egypt. The random forest modeling approach was applied to climatic and land-surface parameters to predict the distribution of ten important plant species in an arid landscape in the northwestern coastal desert of Egypt. The impact of changes in land use and climate on the distribution of the plant species was assessed. The results indicate that the changes in land use in the area have resulted in habitat loss for all the modeled species. Projected future changes in land use reveals that all the modeled species will continue to suffer habitat loss. The projected impact of modeled climate scenarios (A1B, A2A and B2A) on the distribution of the modeled species by 2040 varied. Some of the species were projected to be adversely affected by the changes in climate, while other species are expected to benefit from these changes. The combined impact of the changes in land use and climate pose serious threats to most of the modeled species. The study found that all the species are expected to suffer loss in habitat, except <em>Gymnocarpos decanderus</em>. The study highlights the importance of assessing the impact of land use/climate change scenarios on other species of restricted distribution in the area and can help shape policy and mitigation measures directed toward biodiversity conservation in Egypt.

&amp;lt;p&amp;gt;The Mediterranean region has been identified as one of the most affected global hot-spots for climate change. Recent climate change in the Mediterranean can be characterized by faster increasing temperatures than the global mean and significant decreases in annual precipitation. Besides, important land cover changes have occurred, such as reforestation, agricultural intensification, urban expansion and the construction of many reservoirs, mainly with the purpose to store water for irrigation. Here we study the impacts of these changes on several ecosystem services in the Segura River catchment, a typical large Mediterranean catchment where many of the before mentioned changes have occurred in the last half century. We applied a hydrological model, coupled with a soil erosion and sediment transport model, to study the impact of climate and land cover change and reservoir construction on ecosystem services for the period 1971-2010. Eight ecosystem services indicators were defined, which include runoff, plant water stress, hillslope erosion, reservoir sediment yield, sediment concentration, reservoir storage, flood discharge and low flow. To assess larger land use changes, we also applied the model for an extended period (1952-2018) to the Taibilla subcatchment, a typical Mediterranean mountainous subcatchment, which plays an important role in the provision of water within the Segura River catchment. As main results we observed that climate change in the evaluated period is characterized by a decrease in precipitation and an increase in temperature. Detected land use change over the past 50 years is typical for many Mediterranean catchments. Natural vegetation in the headwaters increased due to agricultural land abandonment. Agriculture expanded in the central part of the catchment, which most likely is related to the construction of reservoirs in the same area. The downstream part of the catchment is characterized by urban expansion. While land use changed in more than 30% of the catchment, most impact on ecosystem services can be attributed to climate change and reservoir construction. All these changes have had positive and negative impacts on ecosystem services. The positive impacts include a decrease in hillslope erosion, sediment yield, sediment concentration and flood discharge (-21%, -18%, -82% and -41%, respectively). The negative impacts include an increase in plant water stress (+5%) and a decrease in reservoir storage (-5%). The decrease in low flow caused by land use change was counteracted by an increase in low flow due to reservoir construction. The results of our study highlight how relatively small climate and land use changes compared to the changes foreseen for the coming decades, have had an important impact on ecosystem services over the past 50 years.&amp;lt;/p&amp;gt;

Distinguishing the impacts of land use and climate change on ecosystem services in a karst landscape in China