Determination of the Absolute Rate of Sea Level by Using GPS Reference Station and Tide Gauge Data

The absolute rate of mean sea level of Xiamen area is derived from the data of Xiamen tide gauge station and Xiamen GPS fiducial station of crustal movement observation network of China（CMONC）. The height variation is discussed deeply in this paper, h is shown that height has periodic variations. So the rate of vertical land movement can not be precisely obtained only from several GPS campaigns. It is pointed out that the vertical crustal movement of tide gauge station should be monitored by using long-term continuous GPS observations.

Vertical motions of tide gauge stations near the Bohai Sea and Yellow Sea

A modified Gauss-Markov model with weighted constraints was constructed by combining satellite altimeter and tide gauge records. Vertical motion rates of nine tide gauge stations around the Bohal Sea and Yellow Sea are estimated. This is the first time systematic estimates have been derived in this region. Downward trends were seen at the six tide gauge stations located at Tanggu, Longkou, Laohutan, Bayuquan, Xiaochangshan, and Yantai; with vertical motion rates of-1.82±0.50, -1.65±0.46, -0.88±0.42, -0.58±0.62, -0.13±0.43, and -0.01±0.43 mm/yr, respectively. Upward trends were seen at the three tide gauge stations located at Qinhuangdao, Huludao and Chengshantou; with vertical motion rates of 1.12±0.46, 0.55±0.49 and 0.26±0.44 mm/yr, respectively. There was significant subsidence in Tanggu and Longkou, and a rising trend in Qinhuangdao. According to our results, the rate of sea level rise calculated from these tide gauge records can be improved using a more accurate measurement of the land elevation accounting for lifting or subsidence. The model derived can be used to estimate vertical motions of tide gauge stations, and can be widely applied to revise the benchmark levels of tide gauges.

Mapping of Stream Flow Trends in Porsuk Basin Using GIS Environment

In this study, trends of minimum, average and maximum flows were investigated in Porsuk basin, which is a sub-basin of Sakarya basin and then changes in flows were mapped using Geographical Information Systems (GIS). In the study, in 10 flow gauging stations across the Porsuk basin, monthly average, maximum and minimum flow data is used covering the period 1961-2013 (53 years). When analyzing the distribution of observed trends in the basin, a trend has been observed in most of the river flows. A decreasing trend has been observed overall in the basin. Trends are generally decreasing over time except for a few stations. As a result, increasing trends are observed in the west part of the basin;while in the east part of the basin decreasing trends are observed. When average and maximum monthly flows are investigated, decreasing trends are observed in the stations except DSI-12182. Trend analysis of 10 flow gauging stations across the Porsuk basin is investigated by Mann-Kendall method. Trend distribution was made according to flow trends of basin by transferring Z values to GIS.