## 4 Results and Analysis
### The Spatial-Temporal Characteristics of Wetland Changes  
From the early 1990s to 2012, the wetland structure in the TRH region has undergone great changes, and the total wetland area increased by 260.6 km\({}^{2}\) or 1.2% (Table 3). Lakes, reservoirs & ponds displayed a continuously increasing trend, but swamps, streams & rivers had a continuously decreasing trend. The area of reservoirs & ponds increased the most, while swamps decreased the most, which was 12 km\({}^{2}\) (77.9%) and 268.6 km\({}^{2}\) (3.3%), respectively. From the early 1990s to 2004, the total wetland area decreased by 170.1 km\({}^{2}\) (0.8%). Among all wetland types, swamps decreased by 242.1 km\({}^{2}\) (3%), which was the largest decrease, while reservoirs & ponds increased by 11.6 km\({}^{2}\) (75.3%), which was the largest increase. From 2004 to 2012, the total wetland area increased by 430.7 km\({}^{2}\) (2%), and lakes increased by 484.6 km\({}^{2}\) (7.3%). From the early 1990s to 2012, the wetland area in the Yangtze River basin showed an overall increasing trend, while in the Yellow River and Langcang River basins, the wetland area decreased in general. In the Yangtze River basin, from the early 1990s to 2012, wetlands increased by 9.8 km\({}^{2}\) (0.1%). The increase of lakes (by 197.5 km\({}^{2}\), 11.8%) was the most obvious, whereas the swamps decreased by 165.4 km\({}^{2}\) (3%). In the temporal change process, lakes continuously increased with an intensive trend,  
Figure 3: Wetlands distribution in the TRH region in 2012.  
swamps and streams & rivers sustained a decline and the swamp decrease has slowed down, while reservoirs & ponds showed little changes. The change of lakes from 2004 to 2012, which increased by 162.2 km\({}^{2}\) (9.5%), was the most obvious increase. From the early 1990s to 2004, swamps decreased by 135.1 km\({}^{2}\) (2.4%), which was most obvious decrease among all wetland types. In the Yellow River basin, from the early 1990s to 2012, the wetland area decreased by 30.7 km\({}^{2}\) (0.6%). The decrease of swamps, which decreased by 82.8 km\({}^{2}\) (4.6%), was the most obvious, and was consistent with the research result of [PERSON] _et al._[9], while reservoirs & ponds increased by 15.8 km\({}^{2}\) (494.1%), which was the most obvious. In the temporal change process, swamps and lakes first decreased and later increased, while streams & rivers and reservoirs & ponds increased continuously. For example, from the early 1990s to 2004, swamps and lakes decreased, and reservoirs & ponds obviously increased. The area of swamps and lakes decreased by 94.1 km\({}^{2}\) (5.2%) and 101.4 km\({}^{2}\) (6.5%), respectively, while in 2004-2012, the reservoirs & ponds showed the most dramatic increase (4.2 km\({}^{2}\), 28.6%). In the Langcang River basin, from the early 1990s to 2012, wetland area decreased by 9.5 km\({}^{2}\) (0.9%). Lakes experienced the most significant reduction, declining 0.3 km\({}^{2}\) (4.3%), followed by swamps which were reduced 9.2 km\({}^{2}\) (2.4%). In the temporal change process, swamps decreased first and then increased, lakes decreased at first and then kept constant, while reservoirs & ponds remained basically unchanged. For example, from the early 1990s to 2004, swamps and lakes were most significantly decreased by 9.7 km\({}^{2}\) (2.5%) and 0.3 km\({}^{2}\) (4.3%), respectively. Figures 4 and 5 show the spatial pattern of wetland changes. From the early 1990s to 2012, the wetland changes experienced a shift from the middle parts to the western parts in the TRH region. Wetlands in the middle and western parts varied significantly during these years.