WP3: MORPH SAMPLING STRATEGY AND CHEMICAL ANALYSIS OF SEDIMENTS IN THE BARASONA RESERVOIR

Transcription

1 SAMPLING STRATEGY AND CHEMICAL ANALYSIS OF SEDIMENTS IN THE BARASONA RESERVOIR PROPOSAL FOR COLLABORATION BETWEEN WP3 AND WP5

2 TECHNICAL DETAILS Description: Sediment sampling and chemical analysis for the Barasona Reservoir and its main sediment inputs (rivers Ésera and Isábena) and outputs (Barasona dam outlet). This report presents the sampling and chemical analysis strategy developed to do a preliminary analysis of sediment fluxes at the Barasona reservoir. Elaboration: WP3 (lead by the University of Lleida and the Forest Sciences Center for Catalonia, UdL-CTFC) in collaboration with WP5 (UB) 1

3 INDEX Summary 3 1. INTRODUCTION 4 2. THE SITE 4 3. SAMPLING STRATEGY Continuous monitoring: river sampling Sampling campaigns: reservoir sampling 7 4. SAMPLE ANALYSIS 7 2

4 Summary This report contains a description of the fine sediment sampling strategy that will be carried out at the Barasona Reservoir with special attention to sediment inputs (i.e., Rivers Ésera and Isábena) and outputs (i.e., Barasona dam outlet). Moreover, a description of the chemical analysis that will be carried out to the taken samples is also included. Sampling strategy has been developed considering some of the monitoring points that WP3 has in the framework of SCARCE; this monitoring points are: i) the River Ésera at Graus (ESE), ii) the River Isábena at Capella (ISA) and iii) the Barasona dam outlet (BAR) (detailed information of these monitoring points can be find at the working document entitled Monitoring Reaches. Proposal for WP3 in collaboration with WP5 ). Collaboration between WP3 and WP5 will be established mainly during sediment sampling and data analysis. 3

5 1. INTRODUCTION WP3: MORPH On Friday 13 th, May 2011, in the context of the SCARCE-Consolider project, a meeting between scientist from UdL-CTFC (Ramon J. Batalla, José A. López-Tarazón and Damià Vericat,) and UB (Isabel Muñoz, Pilar López) was held in Lleida to establish a collaboration framework between the two groups. A pilot study was designed with the objective of studying the transfer of sediments and its chemical characteristics through the Barasona Reservoir. This study includes the sediment input from the rivers Ésera and Isábena, and the output from the dam (i.e., dams releases). Agreement was on defining a working framework that will satisfy the different work packages needs based on scientists expertise. As a result, a sampling strategy was defined to accomplish two objectives: i) establish the basic chemical characteristics of the fine sediment that is deposited in the reservoir and flows out through the dam and, ii) study the retention of C, N and P associated to fine particle sedimentation. A fingerprinting approach based on geochemical determination (i.e., major elements) of the samples will also be applied, to trace sediment contribution of the rivers and the movement of the sediment through the reservoir. The Barasona Reservoir (i.e., responsible of the irrigation of more than 70,000 ha in the Aragon and Catalunya regions) is a splendid study case because of the huge amount of fine sediments that the Rivers Ésera and Isábena deposit on it, threatening its impoundment capacity. This way, the reservoir suffers acute siltation problems since its construction due to the sediment coming, principally, from the Eocene marls (forming badlands) located in the middle part of its draining basin. Engineering works during 1990s to release sediment through the dam bottom outlets resulting in around 9 hm 3 of sediment being sluiced through the dam. Nowadays, the reservoir capacity equals that of 1993 (76 hm 3 ). The reservoir siltation process is a fact that puts on risk cyclically the water resources management and, therefore it requires a special attention from the Ebro water authorities. 2. THE SITE Figure 1a presents the location of the Barasona Reservoir and its contributing basin; it is formed by the Ésera and Isábena catchments, whose rivers drain into the reservoir at the village of Graus. Figure 1b shows a detail of the reservoir area and the location of the monitoring stations instrumented by the UdL-CTFC (within the framework of the WP3 of the SCARCE-Consolider project) that will be used to obtain the sediment that will be later analyzed; 2 monitoring points (i.e., ESE and ISA) are located upstream the reservoir at the outlet of the Rivers Ésera and Isábena, while the third monitoring point (i.e., BAR) is located ca. 1 km downstream the dam outlet. 4

6 Figure 1: a) Barasona reservoir contributing basin; b) Zoom to the Barasona reservoir and location of the monitoring points.

7 3. SAMPLING STRATEGY An integrated sediment sampling strategy including reservoir sediment inputs and outputs was defined. Sampling will be based on: a) continuous monitoring: water samples will be collected at ESE, ISA and BAR (lead by UdL-CTFC); and b) sampling campaigns: drag samples will be collected spatially distributed across the reservoir during different campaigns (lead by UB). A detailed description of the methods is provided in the following sections. Besides, sediment and water samples will be also taken for chemical analysis (priority and emergent compounds). Methodology will be determined by the chemist groups (WP4) and it is not included in the present document Continuous Monitoring: River Sampling Sampling at the monitoring stations will be done using an ISCO 3700 automatic sampler (Figures 2a and 2b). This sampler allows obtaining up to 24 water and sediment samples at a desired time frequency. The sampler will be set up with the objective of obtaining water samples during flood events. These samples will be completed with manual samples taken (weekly or fortnightly) directly from the river during field visits. Therefore, by the combination of manual and automatic samples the whole range of discharge conditions (baseflows, medium flows, high flows and flood events) will be analyzed. Finally, samples will be combined by discharge classes to obtain integrated average samples at each sampling point at a given flow strength. They will be kept refrigerated. Sampling strategy will allow controlling sediment input to the reservoir, by means of sampling at the outlet of the Rivers Ésera and Isábena (i.e., ESE and ISA; Fig. 1b), and the output from the reservoir, by means of sampling at the dam outlet (i.e., BAR; Fig. 1b). Figure 2: a) ISCO 3700 automatic sampler installed at the Capella gauging station (ISA); b) Detail of the collecting bottles of the sampler. 6

8 3.2. Sampling Campaigns: Reservoir Sampling Reservoir sampling will be designed based on a bathymetrical survey that the UdL- CTFC group will carry out during reservoir maximum water level conditions (i.e., ideally June-July 2011). Data will be used to define the optimum location for sampling points. Sediments samples will be taken with a Lenz-type dredge with a 400 cm 2 area. Besides at maximum water level conditions a second sampling campaign will be done during reservoir minimum water level. In this campaign, samples will be taken at different locations presenting dry surface along the reservoir. Chemical characteristics of these dry samples will be compared with those taken before at full conditions to study the effects of the dry/wet periods on sediment characteristics. 4. SAMPLE ANALYSIS Three different analysis will be done: i) grain size distribution, ii) C and N determination at all samples; iii) major elements determination at selected samples. Grain size distribution will be determined with a Beckman-Couter LS 230 particle analyzer in two aliquots: One aliquot will be analyzed directly after dispersion with pyrophosphate and ultrasound, and the other will be treated for organic matter elimination by adding H 2 O 2 Total C, and N will be determined through dry material using an elemental CN autoanalyzer. Also organic C will be determined after acid treatment of bulk sample and further analysis for total carbon. Major elements (Al, Fe, Si, K, Ca, Mg, Ti, Mn, P) will be determined through X-ray fluorescence (XRF) after fusion at 1100 ºC with Lithium tetraborate. 7