Environmental flow assessment of Kayan River: managing sustainability indicator of hydropower project

Nowadays, constructing a new hydropower plant is one of the most attractive solutions to overcome energy requirements. The Kayan Hydroelectric, built in the Kayan River, is projected to generate electricity of nine hundred megawatts. However, the dams have to be managed appropriately since alteration of river discharge will have a significant impact on the environment. This paper proposes an environmental flow assessment as an appropriate indicator to manage sustainability. Three environmental flow assessment methods were used: Flow Duration Curve Analysis (FDCA), Tennant method, and Building Block method. The environmental flow pattern was used as a benchmark to evaluate whether the operation rule of the dams fulfilled the sustainable requirement, particularly on the hydrological pattern of the river. Regarding the Tennant and FDCA method, the minimum discharge that has to be maintained for the minimum environmental flow of the river is about twenty-five cms (corresponds to ten percent of AFF) and thirty-five cms, respectively. Meanwhile, the Building block method informs a range of discharge from a hundred cms to twenty thousand cms during the flood. The environmental flow should be managed to guarantee that the river’s ecosystem and carrying capacity can be preserved.

Application of a hydrological method for determining monthly environmental flow in Code River, Indonesia

The declining groundwater in Yogyakarta could potentially affect the Code River baseflow, thus lowering the river streamflow. Consequently, the riverine ecosystem would suffer from a low quantity of streamflow. The quantity standard of streamflow can be determined by calculating the environmental flow. In this study, the environmental flow requirement (EFR) for the Code River is determined by applying an enhanced version of the most-used hydrological method, namely the Modified Tennant Method based on Multilevel Habitat Conditions III (MTMMHC-III). The EFR in the Code River could be calculated successfully by the MTMMHC-III with a satisfactory temporal variability. The EFRs are the lowest during July to October in the normal years, July to September in the wet years, and July to December in the dry years. The EFRs are highest during January to April in the normal and dry years and January to May in the wet years. However, the EFR might become too low in the dry years, especially from the beginning of the dry season (May) until the early wet season (December), with only 4-11% of the average annual flow. Ultimately, the MTMMHC-III method is a better hydrological method than the original Tennant Method and Q95 method.

Optimasi Pola Tata Tanam untuk Peningkatan Luas Layanan pada Daerah Irigasi Saddang

Daerah Irigasi (DI) Saddang berada di Kabupaten Pinrang Propinsi Sulawesi Selatan dengan luas areal 61.198 Ha, yang mendapatkan air dari Bendung Benteng memiliki debit rata-rata 319 m3/dt dan debit Andalan yang berfluktuasi antara 39,8 – 328,1 m3/dt. DI Sadang memiliki Pola Tata Tanam (PTT) eksisting Padi-Padi Palawija dengan awal tanam yang berbeda-beda pada setiap primer/sekundernya. Hasil perhitungan neraca air dengan PTT eksisting tanpa memperhitungkan debit pemeliharaan didapatkan areal yang terairi seluas 48.958 Ha di MT1 61.198 Ha di MT2 dan 61.198 ha di MT3 atau areal terairi 61.198 Ha dengan intensitas tanam 280%. Guna mengoptimalkan air yang ada maka dibuat PTT rencana, dengan mengeser awal musim tanam pada berbagai variasi. Dari hasil perhitungan dengan PTT rencana Padi-Padi-Palawija didapat bahwa air yang ada masih cukup untuk mengairi areal seluas 61.198 dengan intensitas tanam 300%. Kelebihan air yang ada, jika di manfaatkan untuk penambahan areal, didapat tambahan areal yang bisa terairi seluas 47.016 Ha dengan intensitas tanam 300%. Jadi secara perhitungan total, didapat areal terairi seluas 108.214 Ha dengan intensitas tanam 300%. Perhitungan ini juga tanpa mempertimbangkan debit pemeliharaan. Sesuai dengan peraturan yang ada, debit pemeliharaan tetap harus dialokasikan untuk kelestarian sungai. Perhitungan debit pemeliharaan dengan menggunakan metode Tennant, didapatkan debit pemeliharaan Bendung benteng adalah 31,9 m3/dt. Dari hasil analisa neraca air dengan memperhitungkan debit pemeliharaan didapatkan areal yang terairi dengan pola tanam Padi-Padi-Palawija adalah seluas 61.198 Ha di MT1 61.198 Ha di MT2 dan 16.523 ha di MT3 atau areal terairi 61.198 Ha dengan intensitas tanam 227 %. Terjadi penurunan intensitas tanam sebesar 53 % di banding pola tata eksisting.ABSTRACTThe Saddang Irrigation Area is located in Pinrang Regency, South Sulawesi Province with an area of 61,198 ha, which gets water from the Benteng Barrage, which has an average discharge of 319 m3/s and a fluctuating dependable flow between 39.8 - 328.1 m3/s Saddang Irrigation Area has an existing crop pattern of Paddy Paddy Palawija with different planting starts for each primary/secondary. The results of the calculation of the water balance with the existing cropping pattern without considering maintenance flow as an obligation that must be fulfilled, have a result it can irrigate 48.958 ha in Planting Season 1, 61.198 ha in planting season 2, and 61.198 ha in planting season 3, or irrigated 61.198 ha with 280% crop intensity. To optimize the available water, a planned crop pattern was created, by shifting the beginning of the planting season to various variations. From the results of calculations with the cropping pattern of the Paddy-Paddy-Palawija, it was found that the available water was still sufficient to irrigate an area of 61.198 ha with 300% crop intensity. If the excess water is used for additional areas, an additional area that can be irrigated is 47.016 ha with 300% crop intensity. So in the total calculation, the irrigated area is 108,214 ha with 300% crop intensity. This calculation is also without considering maintenance flow as an obligation that must be fulfilled. Under existing regulations, the maintenance flow must be allocated for river conservation. Calculation of the maintenance flow using the Tennant method, it is found that the maintenance discharge of the Benteng Barrage is 31.9 m3/s. From the results of the water balance analysis with maintenance flow as an obligation that must be fulfilled, from the calculation results obtained that the irrigated area with the Paddy-Paddy-Palawija cropping pattern, was 61.198 ha in planting season 1, 61.198 ha in planting season 2, and 16.523 ha in planting season 3, or 61.198 ha with 227% crop intensity. There was a 53 % decrease compared to the existing crop intensity.

Quantitative Determination of Some Parameters in the Tennant Method and Its Application to Sustainability: A Case Study of the Yarkand River, Xinjiang, China

Analysis of basic eco-environmental water requirements (BEEWRs) along inland rivers characterized by extreme aridity can provide a theoretical basis for sustaining riverine ecosystems stressed by increasingly dry conditions and human activity. In the past, analyzing the ecological base flow as determined by the Tennant method was the predominant method used to calculate the BEEWR of a river. However, some parameter values within this method are determined subjectively, increasing uncertainty in the estimated values. In this paper, quantitative methods for these subjectively determined parameters are proposed and used to analyze the BEEWR of the Yarkand River, Xinjiang, China. The results demonstrate that: (1) the flood and non-flood seasons of a river can be delineated by analyzing the increase rate of monthly runoff as compared to the monthly runoff of the previous month; (2) the ecological base flow standard in the Tennant method can be more quantitatively determined by comparing the BEEWR for each ecological base flow standard to the annual average river loss, where the BEEWR must exceed the annual average river loss; and (3) BEEWRs of other up- and downstream river reaches can be obtained using the formula “BEEWR in the next downstream section equals the BEEWR in the last section minus the river loss between these two sections”.

Quantification of Environmental Flow Requirement for some Rivers in West Java

Sustainable Development Goal (SDG). Water management is making a balance between water for livelihood and water as a resource. Environmental Flow Requirement (EFR) is water conservation, on the side of the water for livelihood, to sustain the river ecosystem. In Indonesia, the common quantification of EFR is dependable flow Q95%. However, there are alternative quantities: a) Guideline of irrigation states that 5% from the available water in the river is for environmental purposes; b) Adoption of the Tennant Method of using 10% of the mean flow; and recently Food and Agriculture Organization (FAO) in the framework of SDG proposed that in Java Island the EFR is from 40% to 50% of the mean annual flow. This paper discusses several ways of quantification of the EFR in Indonesia, and apply the different EFR quantities to Citarum, Cimanuk, and Cimandiri Rivers in West Java. It is concluded that EFR quantity according to FAO that might be suitable for the rivers in the pristine catchments in the southern part of West Java is too high for the rivers in the northern part of West Java which is heavily populated and maturely developed. Furthermore, the dependable flow of Q95% is found to be close to the quantity of FAO, but in the dry season, Q95% is more suitable. It is recommended using a modified FAO that combine with Q95% during the dry season.

Characteristics and Adaptability Assessment of Commonly Used Ecological Flow Methods in Water Storage and Hydropower Projects, the Case of Chinese River Basins

The construction and operation of water storage and hydropower projects affects the structure of water ecosystems of downstream rivers, and the establishment of ecological flow in rivers below the water storage and hydropower projects has significant impacts on maintaining the stability of river ecosystems. A database was established based on 2000–2017 environmental impact assessment (EIA) reports on water storage and hydropower projects in China and ecological flow (e-flow) methods, and the three widely used e-flow methods for water storage and hydropower projects in China were identified on the database. Furthermore, an ecological flow satisfaction degree model was used to evaluate the methods using long series of historical hydrological data from the hydrological stations in the Yellow River basin, the Yangtze River basin, and the Liao River basin. The results showed that hydrological methods are the type most often used for water storage and hydropower projects in China, including the Tennant method, the minimum monthly average flow with 90% guarantee rate method (Mm9M method), and the measured historical minimum daily average flow rate method (MDM method). However, the ecological flow methods selected are not significantly different among different basins, indicating that the selection of ecological flow methods is rather arbitrary, and adaptability analysis is not available. The results of the ecological flow satisfaction model showed that the Tennant method is not suitable for large river basins. The results of this study can provide technical support for establishment and management decisions surrounding ecological flow.

STUDY ON METHODS OF DETERMINATION OF AN ECOLOGICAL FLOW FOR THE MANAGEMENT OF WATER RESOURCES OF THE RIVER BASIN ON MARACAÇUMÉ RIVER

The elaboration of a study on methods for the determination of ecological flow for the management of the water resources of the Maracaçumé River Basin is very important for the proposed use and conservation of these resources insofar as the uses of water, especially the advisory uses, have changed the flow regimes and the existing water availability. In this context, this work aims to discuss about the applicability of hydrological methods that help in the correct and sustainable management of the water resources. In this way, were applied theQ7,10 Method; the 90% and 95% Method, beyond the Tennant Method with ecological flow corresponding to 30% of the average annual flow. The main results obtained were the characterization of the Maracaçumé River Basin and the flow values obtained in each method (0.541 m3/s, 1,075 m3/s, 0,459 m3/s and 19,50 m3/s for the Q7,10; Q90%; Q95% and Tennant (30%) methods, respectively). The work indicates that for the management of water resources in the Maracaçumé river basin, the ecological flow obtained through the Q90 methodology should continue to be adopted, evaluating the possibility of adapting the maximum percentage of use.

A New Ecological Flow Assessment Method Based on Spatial-Temporal Variability and Transferability

To solve transferability and spatial-temporal variability problems of ecological flow (EF) criteria existed in traditional Tennant methods, a new modified Tennant method was proposed. Considering the temporal variability and influence of extreme flows on average annual flow, the EF criteria for every month and water year were set as variables, and median monthly flow was taken as the optimum EF ceiling. Considering transferability and spatial variation of ecological objectives in different water function zones, the mean of monthly flow under 95% guaranteed rate and minimum monthly flow was used as the minimum EF. To avoid arbitrary use of EF criteria at all levels, the idea of arithmetic progression was introduced. On achieving satisfactory verification, the new approach was applied in the Hanjiang River as a case study. It is found that this new approach is reasonable with excellent spatial-temporal variability.