# Shifting of Meteorological to Hydrological Drought Risk at Regional Scale
## 4 Discussion  
Climate change includes the variations in the behavior of climatic parameters, e.g., precipitation, evapotranspiration, etc. [40]. Whereas anthropogenic activities include land-use/land cover changes, irrigation area expansion, increased water diversion, water conservation practices, etc. During the last decades, the Soan basin experienced precipitation and runoff variation (with a change point in 1998 [30]) due to both climate change and anthropogenic activities [30,32]. Based on the drought analysis performed in the current study, notable variations between SPI and SDI values were found over the past three decades. It could be mainly because of major changes in agricultural land, forest, settlement, water bodies, and bare land in addition to natural climate variability [41]. To further justify, a trend analysis of precipitation, runoff, and runoff coefficient had been performed. The analysis resulted, in the case of sub-basin 1 a declining trend in precipitation was observed during the years 1983-2015, as shown in Figure 8a. For instance, the average annual precipitation decreased from 1983-1997 (1950 mm) to 1998-2015 (1570.50 mm). This decline in precipitation was significant in sub-basin 1, while little variation (no significant trend) was found in the case of sub-basin 2 with an average value of 1115 mm and 1065 mm for 1983-1997 and 1998-2015 respectively. For sub-basin 1, the annual runoff depth had a decreasing trend (i.e., an average of 174.44 mm for 1983-1997, and 84.00 mm for 1998-2015) during the study period (left panel Figure 8b) and, the runoff coefficient had no significant trend (left panel Figure 8c). Similarly, in the case of sub-basin 2, runoff depth has a decreasing trend, while runoff coefficient has no significant trend as the \(p\)-value is greater than alpha. The variations in the trend direction of runoff, and runoff coefficient in the case of sub-basins 1 and 2 could be mainly due to land-use changes, e.g., 71 km\({}^{2}\) and 1611 km\({}^{2}\) increase in agriculture land was observed in sub-basins 1 and 2 respectively from 1983-1997 to 1998-2015 [30]. Moreover, the higher decreasing rate in runoff compared to precipitation and change point showed the possible effect of anthropogenic activities [32]. It was anticipated because of a significant increase in the intensity of crops and the construction of large numbers of small dams from 1998- onward [27]. These significant variations were also anticipated due to the significant number of development projects under the Government of Punjab, Pakistan, which comprises the development of ponds and mini-dams for rainwater harvesting and to increase the intensity of agriculture. The initiative of these developments was to increase the storage for crop and drinking purposes, which might have caused the increase in evaporation, and water use for the growing population, ultimately decrease in surface runoff and increasing in probability of drought occurrence. In addition to that, a reservoir could decrease the frequency, duration, and severity of drought events downstream of the dam, and irrigation practices can primarily influence hydrological droughts by consuming streamflow and groundwater, which typically results in a decrease in streamflow and groundwater levels [16,42]. Hence, the Simly reservoir operation, as well as seasonal irrigation practices, could have an impact on the statistical relationship among drought indices. The difference in SPI and SDI trends could be due to evapotranspiration or lag time between rainfall and runoff, which could predict the propagation of meteorological to hydrological droughts. Drought propagation may also be influenced by basin characteristics such as soil moisture, land use, and the relationships between streamflow and groundwater.