Systematic Review on Urban Ecosystem Services in South-East Asia: Asean Countries

Urban ecosystem services refer to all the benefits of nature especially to the urban community and economy for maintaining human well-being. This concept links to the economic, community and environmental aspects and shows how nature conservation is important for human and economic principles. However, the view of urban ecosystem services assessment based on essential categories with current urban development is provided. So, this paper reviews the aim to analyze the types and assessing the categories of urban ecosystem services and the methodological used in ASEAN countries. Furthermore, understanding studies about urban ecosystem services are important in long-term studies for monitoring purpose. As a result, 8 out of 10 ASEAN countries excluding Laos and Brunei have studied urban ecosystem services. In this context, the result also shows the most studies specify the significance of the ecosystem services given by the urban as regulating (waste absorption, climate regulation, water purification, flood regulation, and disease control) and followed by cultural (tranquility, social relations, and recreation). Thus, exploring urban ecosystem interaction in current ASEAN countries may have added benefits in terms of improving the urban ecosystem services to streamline the urban area planning. Finally, we conclude that all the ASEAN countries should play an important role to make sure the countries maintain sustainable and more livable with the right policies and guidelines like can fit in Paris Agreement especially in Climate Strategies and plans.

Efficient Reservoir Modelling for Flood Regulation in the Ebro River (Spain)

The vast majority of reservoirs, although built for irrigation and water supply purposes, are also used as regulation tools during floods in river basins. Thus, the selection of the most suitable model when facing the simulation of a flood wave in a combination of river reach and reservoir is not direct and frequently some analysis of the proper system of equations and the number of solved flow velocity components is needed. In this work, a stretch of the Ebro River (Spain), which is the biggest river in Spain, is simulated solving the Shallow Water Equations (SWE). The simulation model covers the area of river between the city of Zaragoza and the Mequinenza dam. The domain encompasses 721.92 km2 with 221 km of river bed, of which the last 75 km belong to the Mequinenza reservoir. The results obtained from a one-dimensional (1D) model are validated comparing with those provided by a two-dimensional (2D) model based on the same numerical scheme and with measurements. The 1D modelling loses the detail of the floodplain, but nevertheless the computational consumption is much lower compared to the 2D model with a permissible loss of accuracy. Additionally, the particular nature of this reservoir might turn the 1D model into a more suitable option. An alternative technique is applied in order to model the reservoir globally by means of a volume balance (0D) model, coupled to the 1D model of the river (1D-0D model). The results obtained are similar to those provided by the full 1D model with an improvement on computational time. Finally, an automatic regulation is implemented by means of a Proportional-Integral-Derivative (PID) algorithm and tested in both the full 1D model and the 1D-0D model. The results show that the coupled model behaves correctly even when controlled by the automatic algorithm.

Physical and Biogeochemical Characterization of a Tropical Karstic Marsh in the Yucatan Peninsula, Mexico.

Karstic wetlands provide important ecosystem services such as maintenance of hydrological balance, flood regulation, drinking water supply and nutrients cycling. It is important to conserve and maintain karstic wetlands due to its interaction with groundwater systems and its socioeconomic relevance. The objective of this research was to generate base-line knowledge of the microtopography, hydroperiod and biogeochemical characteristics of poorly known tropical karstic marshes by testing two hypotheses, the phreatotrophic nature of tropical karstic marshes, and the alteration of its biogeochemistry by a highway dividing the marsh. The study site is located in the north of the state of Quintana Roo (Mexico), in pseudo-paludal depressions associated to fractures. The water level varied from few centimeters below the ground to more than 100 cm. We demonstrate that the wetland is groundwater-fed with differences among groundwater, interstitial and surface water in almost all parameters measured. The water is calcium bicarbonate type; the main processes occurring are recharge, evaporation and rock dissolution. Our results suggests active denitrification, low phosphates attributed to Ca- and Fe/Al-bound P, elevated alkalinity and sulfate reduction due to anaerobic conditions in water and soil. The soil reflect its sedimentary origin, the bulk density is low with very high water retention capacity. We do not have enough evidence of the highway modifying the biogeochemistry or hydrology of the marsh. These karstic wetlands provide important provisioning and supporting ecosystem services that should be studied, acknowledged and maintained.

Modelling flood regulation ecosystem services dynamics based on climate and land use information

The concept of ecosystem service (ES) identifies benefits that people obtain from ecosystems with contributions to human well-being. One important ES under external pressure is “flood regulation” that describes an ecosystem’s capacity to reduce flood hazards. Several related studies estimate current flood regulation ES. However, regional climate projections indicate a shift in precipitation patterns. Therefore, Climate and land use changes make it necessary to assess future supply in order to test functionality and adaptation measures. This study focuses on surface retention ES. We used two methods to show the relevance of different landscape scenarios and climate information for flood regulation ES supply: 1) hydraulic simulations with the model HEC-RAS 2) the flood retention capacity indicator suggested by the German MAES-Working group. We simulated two events: the historic flood of 2013 and future hypothetically 10% higher water levels. Furthermore, three land use change scenarios were evaluated. The model results indicate water accumulation by vegetation. Higher water levels of future climate scenarios lead to an increase in flooded areas and higher water volumes. To evaluate flood regulation capacities, an approach solely based on 2D retention areas, such as the MAES-indicator, is not sufficient. Modelling approaches deliver the opportunity for future scenario simulations.

Practical work on flow regulation

The Tutorial structure includes the following elements: the concept and meaning of flow regulation, a reservoir and its place in the water management system, the calculations of seasonal and long-term flow management, calculations of flood regulation, determinations both main dam characteristics and the economics of water reservoir control.

Evolution of Flood Regulation Capacity for a Large Shallow Retention Lake: Characterization, Mechanism, and Impacts

The retention lake often plays an important role in flood mitigation through the water storage and the lake–river interactions. However, the evolution of real-time flood regulation capacity remains poorly characterized. Using wavelet decomposition and flood peak removing ratios, this study presents a comprehensive evaluation of the characterization, mechanism, and impacts of the flood regulation capacity in Dongting Lake. The results indicate that the change of flood regulation effect of the lake can be well reflected by the multi-year changes in the variances of the inflow and outflow runoffs. The wavelet decomposition indicates that the flood regulation of the lake is mainly functioned on the high-frequency floods with durations less than 32 days. The average yearly flood peak removing ratios range from 0.13 to 0.56, but no significant tendency changes on the effect of the flood regulation capacity has happened during the study period. The changes in maximum regulation volume reveal that the flood regulation of the Dongting Lake is mainly a passive process decided by the complex river–lake relationship and the interactions among different processes of discharge and sediment. The impacts from the large volume reduction caused by sedimentation in the lake is compensated by the increased flood controlling water level, which in turn have resulted in the new phenomenon of “normal discharge, high water level and disaster” in the lake regions after the 1990s. The significant impacts on the lake–river relationship caused by the sediment reallocation from the operation of the Three Gorges Reservoir (TGR) have further changed the hydrological regimes between the lake and the Yangtze River. Influenced by the new lake-river interaction pattern the discharge passing capacity downstream the outlet of the lake is becoming a key factor that affects the flood regulation capacity, which is leading to a shift of the flood pressures from the lake region to the downstream of Yangtze in the near future.